In 2011 Apple and its iPad continued to dominate, but Android Honeycomb was the big mover. In 2012 Windows 8 is coming, and there's going to be a three-way battle for your money.

In the 200 months in which we've been putting together PC Advisor, one computing platform has stood head and shoulders above the rest: Windows. But the changing size and shape, and the sheer variety, of the personal-computing devices we now use is putting unprecedented pressure on Microsoft's OS. Sure, it still has comfortably the biggest market share in terms of desktop computing, but the real growth and development is in the mobile space. And while Microsoft is still in the process of persuading recalcitrant XP users to shift to Windows 7, yet another Windows refresh is coming down the tracks.

Windows 8: Irrelevant upgrade?

An IDC report recently described Windows 8 as “largely irrelevant” in terms of desktop computing. “Customers will be asking ‘What value does Windows 8 bring to my desktops and laptops?'” warned Al Gillen. He believes access to the app store is the only real benefit.

To put it another way, Windows 7 is very successful although not particularly loved, and Windows 8 is, in essence, simply its predecessor with a bit of ‘mobile' added on. An app store, a Windows Phone interface, and the ability to run on tablets and – potentially – smartphones. So why would people upgrade their desktop PCs and laptops to Windows 8?

In part because of the perceived failure of Vista, PC users have taken to Windows 7. A rough metric, granted, but in the past month 51 percent of visitors to ran Windows 7. Twelve months earlier, that figure was 32 percent. And as of September 2011 Microsoft claimed that it had sold 450 million Windows 7 licences – almost double what it had sold a year before. It might not be sexy, but that's a lot of volume.

Perversely that means it's going to be tricky to push traditional Windows users into yet another upgrade, with all the compatibility issues a Windows update cycle traditionally heralds.

Microsoft is clearly aware of this, and has recently made great play of the fact that Windows 8 will, like Apple's OS X, be available as a download. Indeed, the upgrade process from XP, Vista and Windows 7 will be, Microsoft tells us, a simple process. Visit a website, click a download, cross your fingers.

All well and good. But that the upgrade is relatively easy isn't in itself a reason to make the shift. The truth is, that may not matter. Because as much as Windows 8 is ‘irrelevant' to the desktop, the desktop is much less important to Windows 8. Microsoft has the market share on PCs and laptops, but as the world goes mobile it needs more smartphone- and tablet users in order to stay out in front of Apple and Google. And the key benefit to Windows 8 will be seamless integration of desktop and mobile: a familiar platform across all devices, at work and play (or so Microsoft hopes).

In this Microsoft won't be alone. Mac OS X is long in the tooth and Apple's long-term future might well be iOS-flavoured. And between Google's online apps, Chrome OS and Android, the big G is determined to take as big as possible a slice of your computing life, regardless of what size screen you have. But Microsoft has the massive advantage of being the only OS most people know, which means Windows 8 doesn't have to be a better tablet and mobile OS than Android in order to be a viable alternative.