Microsoft's decision not to support Windows XP users with the next version of its browser, IE9, will raise a few eyebrows. I can't speak for the position in the US, but over here in the UK very few corporates migrated to Vista, and it's the corporate engine that drives IT uptake.
I have anecdotal rather than scientific, researched evidence for this. Last year I chaired an event for Google, which had around 300 CTOs from around Europe attending. It happened to be the day of the launch of Windows 7 and someone in the audience asked who'd be upgrading on day one (answer: nobody rolls out a new OS on day one). But someone from the panel wisely asked who was still on XP. It was a clear majority.
Likewise, recently I edited a supplement on virtualisation that went into the Times in the UK. One of the opportunities a number of the companies I contacted saw was that instead of upgrading all the computers individually companies would opt for desktop virtualisation in order to get Windows 7 moving on the systems after XP. XP? Don't you mean Vista, I asked?
They laughed a bit. No, they didn't, they said, most of their clients would move straight from XP to 7 if they moved at all. And now Microsoft is abandoning XP for future versions of IE.
It'll get a few people upgrading - but I wonder whether the attitude will attract a few more users for Mozilla.