Android 4.1 Jelly Bean.

Good

• Intuitive nature of Google Now
• Butter UI makes swiping silky smooth
• Enhanced notifications

Bad

• Voice search is inconsistent

Although it's only a decimal place update, Android 4.1 is far more significant than Google's shonky version numbering would have you believe. In fact, I'd even go as far as to say it's the most important iteration of the mobile OS we've yet experienced -- but not for the reasons you might initially assume.

In addition to the brand-new Nexus 7 tablet, Google has confirmed Jelly Bean will be landing on the Samsung Galaxy Nexus, the Nexus S and the Motorola Xoom tablet in the middle of July, via an over the air update. Updates for other Android devices will depend on your phone manufacturer and network operator, but don't hold your breath -- many device are still waiting to receive Ice Cream Sandwich.

Jelly Bean may not be officially out for a while, but we've taken the Google I/O 2012 developer version for a spin -- loaded onto the trusty CNET UK Galaxy Nexus, of course -- to see what all the fuss is about, and our impressions are below.

Google Now

Google has made no secret of the fact that it wants to go toe-to-toe with Apple's headline- grabbing Siri voice assistant, and late last year reports were circulating that the folks at Mountain View were working diligently on their own pocket-sized personal pal, provisionally named Majel, after Star Trek creator Gene Roddenberry's wife. It was also widely expected that Google would unveil this new software at this year's Google I/O, but the end result is possibly a little different from what people were expecting.

Google Now is part personal assistant, part knowledge centre. Voice control is a big part of the appeal, but you can actually get a lot out of it without ever having to utter a single word. Google Now can be accessed directly from the lock screen, or by pressing and holding your finger on the home icon at the bottom of the display. You can also boot it up by tapping the newly- designed Google Search bar, which remains pinned at the top of the screen -- just like it was in Ice Cream Sandwich.

As soon as Google Now opens, it bombards you with useful info. This is displayed as a series of cards, which can be scrolled through vertically and dismissed with a horizontal swipe if you feel they're not relevant. This is the clever bit -- these cards are context and location sensitive, and also incorporate your web history to offer up the kind of data you genuinely need.

Google Now can perform weather searches by detecting and using your current location.

Before I even had chance to try Jelly Bean, I performed a search on my desktop computer (a Mac, ironically) for a route map to a place I intended to drive to the following day. A few hours later, I opened Google Now for the first time and bingo -- there's a card which shows the location I searched for, plus the estimated journey time and distance in miles. To top it all off, Google Now even presented me with a mini-map, and a link to Google Navigate, allowing me to effortlessly obtain the driving directions. Now that's clever.

This is just one small example of Google Now's power. By looking at your location, it can display public transport times or places of local interest. After a while, Google Now learns the route you take to commute to work, and can therefore inform you automatically when traffic incidents are likely to impact your trip home. Some people would call all this knowledge gathering covert or slightly creepy, but it only takes a few days with Google Now to realise it's actually incredibly useful, and possibly one of the most intuitive elements of Android yet seen.

Voice Search

Another aspect of Google Now is Voice Search -- which is essentially the 'Siri' part of the app. Like Apple's software, Voice Search is able to respond intelligently to natural questions, such as 'How old is Tony Blair?' or 'How many inches are in a foot?'. On the whole, the system works well -- in fact, its actually faster than Siri when it comes to getting the data you need.

I noticed some annoying inconsistencies however with the way Google Now's voice search handled some of my questions. For example, asking 'How far is the Moon?' gave a voice response, plus an on-screen distance in miles. However, asking the same question but with 'Pluto' in place of 'Moon' merely brings up the default Google web search results -- Google Now's 'fall back' option when it can't reply in a human-like manner. It's not entirely clear why this should occur -- unless of course Google has pre-programmed replies to what it believes will be popular questions, which is sort of cheating.

Google Now's voice search is speedy, but watch out for inconsistencies.

I also noticed that some functions such as text messaging, calling people and setting alarms and timers didn't work for me, despite the fact that many other Jelly Bean users have reported success with these functions. This could be something to do with region issues -- Google has already vaguely alluded to the fact that Google Now doesn't provide full functionality outside of the US. The UK female voice is also a lot more robotic-sounding than its smooth-talking US counterpart.

On the whole, the Voice element of Google Now is actually a bit of a letdown. While it does some things better than Siri, it feels half-finished -- in the UK, at least. It's important to point out -- lest we forget -- that Siri is also bound by location-based issues, with UK users unable to use Siri to search for local business or locations.

Butter UI

While Google Now might be the most obvious new feature of Jelly Bean, for me, the stand-out inclusion is Google's Butter UI. As something of an Android fanboy, it has always pained me that iOS is so much smoother and more responsive than Google's OS. I always convinced myself that this was a trade-off for enhanced functions and multi-tasking, but secretly, I coveted the silk-like interface of my iPhone-owning chums.

Those pangs of jealousy can now be put to bed, because Jelly Bean is as smooth as a baby's posterior. The Butter UI is all about increasing CPU power when your finger makes contact with the screen -- so swipes are recognised instantaneously, rather than with a delay, as was often the case with previous versions of Android.

This simple change revolutionises how Android feels -- there's no lag, no delay and no awkward pauses. The entire OS is enriched and improved beyond measure and even makes 4.0 look sluggish -- which is quite something when you consider how much of a step up Ice Cream Sandwich was from Gingerbread in terms of user experience.

Access galleries of pug photos within seconds with the silky Butter UI.

Google has also worked hard to ensure that there's no lag when opening up applications or switching between various sections of the UI. Ice Cream Sandwich vets will no doubt concur that opening the multitasking menu sometimes took seconds -- in Jelly Bean, it appears instantly.

It's not a complete break from the past -- there are still odd stumbles and pauses, but these are usually in third party applications which haven't yet been optimised to fully support Android 4.1. On the whole, Butter UI is a revelation -- and in my opinion, the most striking aspect of Jelly Bean by far.

Enhanced Notifications

Apple has been playing catch-up with Google when it comes to notifications, and pretty much ripped-off the Android system in iOS 5.0. In many respects, Apple managed to better Google's system, loading up the iOS Notification Center with additional data which made it even more useful.

Jelly Bean's notification system is better than ever.

The pendulum has now swung back in the opposite direction thanks to Jelly Bean. Google has overhauled the existing Android notification system and made it even more adept. You can now see additional information on emails, including a list of your unread messages. By holding two fingers over an email and pulling them apart, you can get an expanded view, showing the contents of the message without even having to open up Gmail.

It's also possible to react and respond to notifications without actually having to fire up the relevant application. For example, if you take a screengrab, it appears in the notifications panel with a link to share it instantly.

Not many third-party programs support this feature at the time of writing, but that's understandable when you consider that Jelly Bean isn't technically released yet. Once July comes around, expect to see many popular apps boasting quick-access functions direct from the notification bar.

Outlook

In addition to better notifications, a smoother interface and Google Now's impressive ability to learn your every move, Jelly Bean has a few more minor enhancements. Arranging icons and widgets on your homescreen is easier, thanks to the fact that other icons shift aside automatically depending on where you drag your new item.

Simplified widget arrangement and better notifications are just a few of the enhancements that can be found on Jelly Bean.

There's also a slightly different 'Share' menu, faster camera performance, a more accurate keyboard (complete with SwiftKey-style word prediction) and secreted deep down in the bowels of 4.1's developer menu you'll find the ability to protect your USB storage to prevent unwanted applications from accessing it.

Speaking of irksome apps, it's also now possible to completely suppress notifications from certain programs -- especially handy if you have Draw Something installed and want to put an end to all those pesky update messages.

I have to admit that Google has really surprised me with Android 4.1. I wasn't expecting such a dramatic change, and to be honest, a cursory glance at the feature list doesn't suggest that it's really that big a deal. It's only when you scoop up a device running Jelly Bean that you appreciate just how different this update makes Android feel -- everything is smoother and faster, and that on its own makes this one of the most competent updates I've yet witnessed from Google.

Jelly Bean is about refining the Android experience rather than adding tons of new features.

For once, the search giant's development team has wisely decided that the quality of the experience is just as important as how many new functions have been added.

Of course, there's no way we can be sure that the same level of performance will apply when Android 4.1 is pushed to phones with single-core CPUs (like the Nexus S, which will get an OTA update at the same time as the dual-core Galaxy Nexus in July), or how it will react when a third-party UI skin -- such as HTC's Sense or Samsung's TouchWiz -- is slapped on top of it.

Moving forward though, every new Android device will benefit from Butter's vastly superior performance and Jelly Bean's enhanced functionality -- which bodes well for the future of Google's OS.