I go where the games are, man. Believe me, I'd much rather have not bought one (my dislike of MS is well documented), but I got tried of waiting on games to show up months or years later on the PC, or sometimes not even at all...
I've been a dual PC Gamer/console gamer since 1983. Nothing quite like growing up in the 80s with a Commodore 64 in one room and an NES/Atari2600/Coleco setup in the other. Granted, I'm biased towards PC, but I've always given both a fair chance for my dollar.
With all the vista nonsense, I've since promised myself to abandon the PC as a gaming platform. My Xbox360/Wii will be where I get my gaming fix from now on. Well, until I want to fire up Exult or DOSbox.
As for this new "XP" version...I have a friend who, last month, showed me a hacked version of the Vista Geometry Wars that was made to run on XP. He's been playing it everyday since then. Funny that all of a sudden an XP version pops up on Steam.