I don't think they're out to take over the OS market like Microsoft did because they're first and foremost a hardware company with an entirely different business model.
They've been doing better than ever the past couple years. I think they've got around a 20% market share now which is pretty remarkable.
It's actually
4-8%, which, while showing a gradual increased adoption over years, is still not a threat to the 90-95% dominance of Windows PCs. Most people who didn't like Vista kept or downgraded to Windows XP, and I'm sure Microsoft will try to make Windows 7 a better experience than Vista. They don't have to worry yet.
An interesting trend that might open a new market for alternative operating systems is
netbooks, small and cheap laptops used mainly for browsing. Some of these laptops are already running versions of Linux, as well as Windows XP. For most users whose main interaction with computers include checking e-mail and Facebook, they are a good investment and they wouldn't miss Windows much. I wonder when Apple is going to start targeting that market.
I personally don't mind Vista, I believe most of the concerns are a bit overrated, but that's mainly because I rarely run into driver or software compatibility problems and my machine is fast enough for me not to notice any harmful performance hit. Still, my main operating system is Ubuntu and I mostly use Vista for games, so I guess I haven't used Vista enough to hate it.
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The Decline Of Microsoft and the Proposed Rise of MAC