To further that comment, there's a "aftermarket" version of XP called "XP Performance Edition" available on various Torrent networks that strips out almost all of the crap included in a standard XP package these days (legacy drivers, Windows Messenger cruft, etc). I can't recommend this highly enough - it is super fast and I know it's not bogged down with things that will slow down a brand new PC needlessly. ANY new PC I get now is wiped clean and gets this Performance Edition loaded immediately.

While I have no real objection to Vista, I simply do not want to go through the hassle of using drvers that are still effectively in Beta for many products. My scanner and printer for example still haven't ironed out Vista driver bugs. For no practical benefit, why would I bother with Vista when the XP drivers work perfectly. (Same goes for 64-bit OSes as well)