What Microsoft are missing is a killer feature. Sure Vista looks prettier but all that bad press about cancel/allow and high-end hardware mean people will upgrade when they buy their new system.
Businesses are taking the safe option and using their downgrade rights to keep XP uniform on the desktop.
I have a new shiny Dell machine with Vista Business downgraded to XP, for fun I installed Vista and compared it to XP. No real difference, work is not quicker, pretty doesn't make any difference in Excel (Calc but still!).
Kubuntu however loves it, as you may guess I am using 3.5 and without Compiz and it really flies. Of course there's no antiviurs or spyware scanner.
Overall I am using Kubuntu for everything except games, which XP does nicely. In time I may have to switch to Vista, through strong-arm tactics like DirectX compatibility, but for now Vista is not for me.
I speak to a lot of IT and non-IT people and it's the IT ones who are not upgrading. This in turn effects their users who are convinced that if "Tim the IT guy" says Vista is crap, they'll keep XP at home too.
Bill, 'cause it's all down to him.