Version 4.0 started life as Ice Cream Sandwich, but the last three decimal additions came under the Jelly Bean banner. This new version was obviously deemed different enough to snag a new nickname, but not different enough to merit a jump to version 5.0. With version 5 now emerging as Android Lollipop, which is set to launch imminently.

That 0.1 bump hardly does it justice though. Don't be fooled: this is an important step up for Android. KitKat is super-smooth, the UI is refined and elegant, there are improvements to the long-neglected calling and messaging side of the platform, a new focus on productivity, and your fortune-telling digital assistant is brought front and centre as Google Now reaches maturity.

General surprise in the tech world wasn't just based on the erroneous supposition that Key Lime Pie had to be next; there were also some raised eyebrows at the idea of Google entering into a tawdry cross-licensing deal with Nestle which would see a flood of Android-shaped KitKats hitting the shops offering buyers the chance to win Nexus 7 tablets or Google Play credit.

According to Google the promotion was its idea, and no money changed hands. With Nestle producing 50 million Android KitKat bars it certainly looks like a sweet deal for them.

Naming conventions aside, the 4.4 update is about addressing some of the Android criticisms that simply won't go away, and it does so very well indeed.

There's a real focus on the consumer here, with a smattering of useful new features, a noticeable bump in performance, and some optimization to ensure that budget hardware is not left behind.Android 4.4 is easily the best version of the platform to date, and Google has left the ball firmly in the OEMs' court when it comes to rolling out the upgrades.

Leading the field by extending the update beyond its Nexus line to the Moto G also neatly illustrates the move to improve the Android experience on low-end, affordable hardware.

Android KitKat started out as version 4.4, but it's since had various small updates in the form of 4.4.1, 4.4.2, 4.4.3 and most recently Android 4.4.4 - this review has been updated to reflect the tweaks and changes experienced at each step to give you the most complete overview of the operating system, as well as highlighting how things will change in the move to Android 5.0 Lollipop.

KitKat really makes a mockery of the idea that iOS 7 is more refined than Android and even stands up well toiOS 8. This version of the platform is impressively fast, with stylish transitions and an intuitive feel that masks the potential complexity.

There's a paring back of the notification bar that introduces translucency and context awareness, enabling you to reclaim every pixel of your display for whatever you're doing.

There are a few new features here, and not all of them are perfect, but for the most part Google has cherry-picked improvements and refined them.

The contrast between the bloated OEM launchers and stock Android could hardly be starker, but there are still a few things that manufacturers like Samsung and LG could teach Google (split-screen apps is an obvious one) and some of these things will be addressed in Android Lollipop.

The familiar white Google logo, followed by four pulsing colourful circles, still greets you on booting up, but the process has sped up dramatically as the platform has matured. When I checked version 4.1 on a Galaxy Nexus it took 34 seconds. The Nexus 4 running Android 4.2 Jelly Bean clocked in at 19 seconds.

Android 4.4.4 took around 20 seconds to boot up on the Nexus 5 used for testing. Not quite as fast as the Nexus 4, but when you consider that my Galaxy S3 running version 4.3 of Android took just shy of 40 seconds to boot up, you get a feel for how speedy that is.

As the home screen comes into view, you can immediately detect the lighter feel that Google was shooting for. The status bar icons at the top are now white.

The custom Roboto font looks like it has been on a diet, which makes it feel that little bit more crisp and elegant. Looking at menu highlights and icons, what once was blue is now generally grey.

All of this is set to change again though with Android Lollipop, which will be giving the OS a 'Material Design' makeover which gives it a flat look while making everything that little bit more real.

The changes go further on the Nexus 5 because it has the Google Now Launcher. Those black bars top and bottom are gone. A subtle gradient is retained to ensure white icons are clear, even on light backgrounds.

Head into your app drawer and you'll find white dots at the bottom of the screen to illustrate which page you are on. The icons are now much bigger and clearer, at the cost of displaying just four across instead of five.

The widget tab has been dumped, and you won't miss it because a long press anywhere on the home screen gives you access to the widget menu, as well as wallpapers and relevant settings.

Swipe from right to left and you can access additional home screens. There doesn't seem to be any limit, you simply drag an icon to the right to create a new screen. Any home screen you empty will automatically disappear.

The only real surprise is that you have to scroll deliberately through each one; you can't take a shortcut by tapping on the page marker dots at the bottom.

Swiping from left to right on the home screen will bring Google Now into view, but I'll go into that in more detail later.

Initially none of these changes made it beyond the Nexus 5 by default, but the Google Now Launcher has since been made available for other devices in the Play Store.

I was disappointed and surprised that Google initially decided to keep this as a Nexus 5 exclusive, so it's pleasing to see it getting a wider release.

If it doesn't work for you, the good news is that popular launchers, such as the free Nova Launcher, can be used, and the status bar transparency is supported along with a number of other customization options, to help you get the look you want.Jelly Bean saw a major overhaul of the notification shade, but dragging it down from the top of the screen won't reveal any major changes in KitKat.

Google has moved on to the next challenge, and refreshingly there has been some overdue attention lavished on the calls and messaging apps.

Though notifications will be returning to the spotlight in Android Lollipop, as that enables them to appear on the lockscreen and become less intrusive by popping up at the top of the screen when you're in an app, rather than blocking your view.

The Phone app sits bottom left in the dock on your home screen (although the dock can be customized to your liking). Fire it up and you'll find that frequently contacted people are prominently displayed.

There's a search bar at the very top for contacts or nearby places, and it auto-suggests as you type, so you'll rarely need to input more than a couple of letters.

Your last call is highlighted at the top, with three favourites below that, and then the rest of your contact list. It only fills this in as and when you call people.

Three icons sit in a blue bar at the bottom: on the left you have a call log, in the middle there's the dial pad, and on the right is where you can add, import or export contacts, and access call settings.

The caller ID system has also been improved, so that it can automatically search for businesses with a matching number in listings on Google Maps, if the phone number calling you is not listed in your contacts.

There's nothing Earth-shattering going on here, but Google's bet that most of us only frequently contact a small group of people is a safe one, and it makes the Phone app faster to use.

The changes to the messaging system are much bigger. Google has decided to consolidate MMS and SMS messages into its Hangouts app.

When Android 4.4 KitKat initially turned up I was pretty critical of the Hangsouts app, as the separation of SMS and Hangout messaging threads and the lack of auto-detect to choose how to message a contact, felt awkward.

Thankfully I can now say, with Android 4.4.4 running on my Nexus 5, the whole experience is a lot better. Both of my primary concerns have been addressed by Google and Hangouts is now a slick, fluid messaging application.

If the person you want to contact is online and signed into Hangouts (via Google+, Google Talk or Gmail), then you can use that service. If they aren't, your phone will automatically detect that and switch you to SMS mode.

You can choose between available options by tapping the icon to the left of the text input box - allowing you to over ride an online instant messaging chat in favour of a good, old fashioned SMS.

The Hangouts app allows you to share your location, which is great for meeting friends, and you can send files like animated gifs, or make video calls. Google has also integrated Emoji into the keyboard, so you have a huge list of comical Japanese squiggles to make your messages more interesting.

Just remember that they won't display properly at the other end if the person you're talking to doesn't have Emoji characters installed.

It's commonplace to use your smartphone for work nowadays, and there's a greater level of expectation that it will be able to handle documents. The days of the BlackBerry device for the office and something else for home are long gone.

Google has included QuickOffice as a standard app with Android 4.4. It enables you to create and edit Word, Excel and PowerPoint files on your phone or tablet.

You can save those files to the cloud using the 15GB of free storage you get with Google Drive. It's also capable of opening PDF files. You can share any of your creations directly via email, Bluetooth, Google Drive, and other cloud services.

There's a new Cloud Print feature to simplify the process of printing a photo, document or web page wirelessly from your Android smartphone or tablet.

It's a pretty barebones option, and you'll need to use a printer that's connected to Google Cloud Print or an HP ePrint printer. Other printers will add support via apps in the Google Play Store.

It draws the list of devices from Chrome, so any device or printer you've used while signed in on Chrome gets listed. This might be a headache for some, so you're best off going to the Google Cloud Print website, when signed into your Google account on your desktop, so you can set it up exactly the way you want.

There's no denying that Google tries to push you towards using the services it wants you to use, and Gmail is a good example. The improvements to the Email app in Android 4.4 offer a welcome break from this pressure.

Some of the better features of Gmail have been integrated. Emails are organized into nested folders, contact photos are displayed, and they double up as checkboxes to select messages.

The bottom navigation bar is gone and there's a new slide-out menu that comes in from the left, offering access to all your folders.

You can also just slide an email left or right to delete it, which enables you to get through that inbox faster. The only obvious thing that's lacking is threaded email conversations.

It looks like Google might allow the Gmail app to handle non-Google emails with Android Lollipopthough, so having two email apps may soon be a thing of the past.

One final boost to productivity is offered by the revamped Downloads app. If you download a lot of files this will really help you find what you want without a lengthy search. You can choose between list or grid view, and you can filter by name, date, or size.

You'll also find that the menu that slides in to enable you to open files in specific apps and attach them provides you with a clear choice of recent files, cloud services, and downloads.

The allocation of 15GB of free cloud storage is fairly generous, provided you don't mind using Google services. There are various routes into that space. The most useful feature is the auto-backup for photos and videos. You can set it up via Google+, the Photos app, or Google Drive.

You'll also find that you can open your Google Drive files directly from the cloud in relevant apps. Use Quick Office and you can open Word documents.

Fire up the Photos app and you can see photos and videos taken with the camera on the device you're holding, or tap the Highlights tab and you'll see all of your photos and videos from any device that you've backed up, as well as photos you've posted in Google+ and photos you've been tagged in on Google+.

When it comes to viewing your photos and videos, Google is clearly transitioning from the old Gallery app to a new Photos app. That means there's a slightly confusing mixture of the two.

The Photos app looks fresher, with a white background and a nicer layout.

It lists your content chronologically by default. It pulls in all of your backed up content from Google+, and supports Auto Awesome photos and movies.

The photo effects allow you to merge photos, create wee animations, and more.

There's also an editor to create movies from a mix of photos and videos with various themes, styles, and background music options. The real attraction is the "auto" part of the equation, but you'll have to tweak to get really good results.

The Gallery app has a more in-depth photo editor, but none of the Auto Awesome features. It has a traditional album set up by default, but you can choose to filter by time, location, people, or tags.

Both of the apps duplicate sharing functionality, although it's an option that looks more stylish in the Photos app and you can see the extra integration with existing Google services.

It's another area where Google is trying to tempt you into using its services with some interesting and exclusive features, but the Gallery app is perfectly functional and you can afford to ignore the Photos app if you prefer not to use it.

On devices from other manufacturers there's a good chance that the stock Gallery app will be replaced by their own app for photos, and that's part of the reason it has to be there. It remains to be seen how, when, or if Google will integrate the two in future.

Bear in mind also that the look if not the functionality of all these things is going to change with Android Lollipop to fit with its new Material Design.

The pre-emptive powers and general usability of Google Now are improving with every passing Android release. On the Nexus 5, or any other device running the Google Now Launcher, you only have to swipe from left to right on the home screen to open Google Now.

On other Android 4.4 devices you can swipe up from the Home button, wherever you happen to be, and whatever you happen to be doing, and it will launch.

As long as you have your language set to US English (you'll find the option to change it in Settings > Google > Search > Voice) you can simply say "Ok Google" to launch a voice search and you can do that from any screen on the phone, even the lock screen.

You can use Google Now for all sorts of thing, including web searches, sending messages, making calls, launching apps, and even playing songs.

The one impediment to that is the speech recognition, but it's showing real signs of improvement in Android 4.4. Even with my Scottish brogue the success rate for queries was pretty high. You can also tap on any wrongly interpreted words and pick a replacement from the dropdown list.

Google is apparently working on integrating Google Now with partner apps next, so it will be able to access their content, and that could advance it another step.

The customization options are still very limited right now, and if you aren't interested in weather results, commute updates, specific sports teams or stocks, then it's just about the voice commands.

Android has been criticized for lag and stutter since it first appeared on the mobile scene. This is somewhat inevitable when you allow low-end hardware to run the platform and manufacturers to create their own user interfaces. Project Butter was the concerted effort to eradicate lag in Jelly Bean and it definitely worked, but KitKat takes it to a whole new level with Project Svelte.

Navigating around on the Nexus 5 or Nexus 7 is lightning fast and silky smooth, nary a touch of lag to spoil your day. The Nexus 5 has had special treatment to ensure that the touchscreen is responsive and accurate, and you can really feel the difference.

Any device with Android 4.4 will benefit from the memory optimization, and if you're on Android 4.4.3 or 4.4.4 there are even more improvements, making it a breeze to skip in and out of apps and games. This speedy performance is no surprise on a powerhouse like the Nexus 5 or Nexus 7 with their 2GB of RAM, but it really stands out on a device like the Moto G with 1GB of RAM.

That's what makes KitKat so important for the budget end of the Android market.

Google's Project Svelte enables the platform to run reliably on devices with just 512MB of RAM. It could be a viable update for devices stuck on Gingerbread.

A 'low memory' mode can automatically scale back animations and ensure that the hardware can cope. The real barrier to this is persuading manufacturers and carriers to update old devices when they'd prefer you to buy a new one.

There should be even more performance improvements with Android Lollipop, in large part because it switches to the ART runtime, which is both faster and more memory efficient than Dalvik, which is the standard Android 4.4 runtime.

Better yet, Android Lollipop should also bring improvements to battery life as well as a battery saving mode to keep your devices going for as long as possible.We've covered the highlights already, but there are a few other enhancements worth mentioning. For a start, KitKat finally brings lost device security to the platform as a default. The Android Device Manager, for finding and remotely wiping a lost device, is now built in to the platform.

When you are listening to music on your device, or projecting movies to Chromecast (now fully supported), you can enjoy full screen art and controls on the lock screen.

The immersive mode which melts the status bar away when you're playing a game or watching a movie is available for all apps now, although it will require developers to update them to support it. A simple swipe up from the bottom of the screen conjures up the Back, Home, and Multitasking keys.

It's also truly gratifying to be able to check your notifications by swiping down from the top of the screen without having to exit whatever you are doing.

Notifications should get better still with Android Lollipop, as among other things it will smartly prioritise them based on your own usage.

Bluetooth MAP support in Android 4.4 promises better integration with Bluetooth-enabled cars, closed captioning and subtitles can now be turned on via the Accessibility menu, and you can manage Home screen replacements or launchers from the menu via Settings > Home.

Perhaps the biggest new feature we haven't mentioned yet is support for tap to pay via NFC. Google has found a way to allow apps to manage your payment information in the cloud or on your device, so you can use Google Wallet, even if carriers are trying to push their own alternatives.

Throw in support for IR blasters, a more power-friendly way to act as a pedometer, and a new location option in quick settings to give more control over what apps are tracking your location and how they do it.

All in all there are a lot of little tweaks and additions that improve the whole experience, though it's a shame that things like low-power audio playback and HDR+ photography have been limited to the Nexus 5.

The emergence of that Google launcher makes you wonder how much further Google's Android might deviate from the stock experience on other devices in the future.