To the guy who said that XP was slow and had no search bar - XP runs much faster on my PC, and the search feature is the most annoying in my opinion, because I don't lose much anyway, and when I do, I use a faster method than winXP's search - cygwin's "find /cygdrive/c/ | grep LostFile > somefile && notepad somefile"
I think that XP is the best, especially as it has no built-in DRM, it doesn't treat you as a baby (like vista does, "are you sure that you want to run this program that you clicked on like 6,000,000,000 times? because I don't care, I'm just here to pop up an annoying box telling you you're an admin and asking you if you want to do what you said you wanted to do.")
XP (like linux) is more for the no-questions-asked approach.
Compare:
Clicking installers in XP
sudo ./install in linux
Clicking installers, waiting for the box to appear, blocking out every other program, clicking continue, and then it runs - in vista.
I think, though, that each is targeted at a different market. Any serious computer user should get XP, while most computer-illiterate or basic-level computer guys should dabble in the shallow paddling-pool that is vista.
Damn, I miss linux. I'mma get an ethernet card off ebay - because it gives me hell with all ralink drivers.