The world’s computers run almost entirely on Windows, and with the latest version of the software Microsoft is planning its biggest revolution in nearly 20 years. It’s essential, because computers have changed almost beyond recognition, but it’s a huge gamble too.

With Windows 8, Microsoft must retain the loyalty of the customers who already use XP, Vista, Windows 7 and other variants, but it must also challenge Apple and Google, whose tablet operating systems threaten to overhaul the way many people work and play.

Microsoft’s solution with Windows 8 is to have both – a tablet operating system that it calls Metro sits alongside a fully fledged version of Windows 7. So for now if you want to run Word or Photoshop, for instance, you’ll use the existing desktop versions, but if you just want to casually browse the web, then Metro will be the better place to do it. Should Adobe bring their excellent Photoshop app to the Windows 8, however, you may be able to use it in Metro too.

The ‘desktop’ mode, formerly Windows 7, looks like Windows 7, with the exception of the Start Menu. It’s gone. Existing users will ask why, because it is where so many things, including shutting down, start. Microsoft now expects users to search for files or access them through programmes directly. I quickly became used to the absence of the menu, but I couldn’t help wondering why Microsoft felt the urge to make me.

Metro, however, is a different beast altogether – it’s startlingly different from anything Microsoft has produced before, and although it has many features in common with Windows Phone it is considerably more advanced. In this new Release Preview, Metro has been tightened up exponentially compared to the previous, Consumer Preview. It moves with effortless speed, and swiping menus on from the side of a tablet device becomes totally intuitive very quickly. Microsoft says 82 per cent found their way around the whole system within an hour. The changes between the two iterations are fundamentally in tuning rather than in major additional features.

What’s consistently striking is how lovely apps look, whether that’s those built by Microsoft to do simple thing such as show mail or the weather, or those built by a growing number of third parties such as Amazon (or the Telegraph). All of them integrate sharing comprehensively and use a similar set of prompts – swipe from the bottom to bring an app’s own menu up, swipe from the right to bring the ubiquitous menu for settings, sharing and search. Swiping from the left of the screen switches between apps.

Microsoft now clearly expects users to find most of what they want either pinned to their own homescreens, mobile phone style, or through that search menu accessed by swiping on the right. This sounds different to Windows 7, but in fact I found it similar to how I use the current OS – a shortcut to Microsoft Word is easily accessible because I put it on my desktop, but Powerpoint is less conspicuous because I use it less. Searching, in 7 and 8, is the easiest way to find it.

One major improvement is the addition of what Microsoft rather off-puttingly calls ‘Contracts’. In fact these are simply ways of making apps talk more easily to each other – a simple piece of code, Microsoft claims, will allow users to search in apps, providing a useful filter if, say, you’re searching for a piece of music. The operating system acts as a broker between users, apps and functions, and it works really well.

Much-vaunted features such as semantic zoom remain intact, too, so if you pinch out on, say, news on a football club it will take you to football news in general. This, part of the new Sports, Travel and News apps, is a great addition.

It’s tempting to characterise the split between Metro and Desktop as between work and play, but that’s not quite fair. You should expect to see a number of tablet applications in use by workers selling products or managing supply chains and workflows. The Metro operating system suits these better. Some users have suggested that trackpads simply won’t be as good as tablets for Windows 8, but new drivers make trackpads behave like the screen of a tablet; swipe from one side to bring up similar menus. That too seems like a new standard. New, improved hardware will arrive with the launch of Windows 8 proper, later this year.

There are other iterative improvements: the software will need rebooting just once a month, and it feels familiar where it should and easy to pick up where it isn’t. Interoperability between devices – which will now, for instance all know a wifi password once you logon once – is just one example of a series of such new features, while Metro and its apps, with their live tiles constantly displaying the latest information, offer a whole new paradigm for Windows. Although initially the tiles are dominated by Microsoft, users can resize them, remove them and of course add their own apps.

It remains to be seen how that will actually work, but it feels futuristic for now. In the few days I’ve had with a tablet and a keyboard dock, Windows 8 already feels stable, but it needs more apps. Microsoft says that they’re coming. What’s surprised me most is using Metro with a mouse is possible and not too annoying. Nonetheless, the main advantage for Windows 8 comes with the new, lovely tablet interface. For laptop users thinking of upgrading from Windows 7, it seems likely that Windows 8 will offer a set of extra, impressive features, but it is hard to argue they are yet compelling. As more people adopt tablets for more tasks, however, that is likely to change. Metro is already as impressive and more intuitive than Google’s Ice Cream Sandwich, and a competitor for Apple’s iOS. Microsoft may yet, surprisingly, have timed its operating system’s vital transition just right.

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