I only recently (< 1 year) got over my XP phobia, so it'll be a while before I welcome Vista with open arms. (and even then, it probably won't be open arms, but rather a grimace).
I managed to force XP onto my old machine, a AMD K6-2 350 Mhz- when I did, it only had 2GB of HD space, and a measly 96MB of RAM. needless to say I was kind of forced to disable themes). At the time it wasn't even capable of using OpenGL, what with it's ATI 3d Rage Pro 8MB (Why do I remember all this?). I slowly upgraded that computer to the max- 32GB drive, 512MB of RAM, Radeon 9250... then I realized that I should probably just get a new computer. And I did, an empty shell (essentially) from a PC repair shop- I got it for 200$, probably wasn't worth that much, but oh well. What OS did I install? Why XP of course!
Although I still use PC-DOS 2000 on my Thinkpad 755CDV along with windows 3.1