Because Vista is a fucking fantastic operating system, plays games better than XP, without limiting my hardware options while charging me up the ass for it.
Besides, like Mac fanboys are the ones to talk - Apple shoves another $120 service pack down your throats every 1-2 years.
Just like any new operating system, there is a learning curve for the first little bit. Since you don't use the operating system, for "obvious" reasons that you don't disclose, leading me to believe that you're just another FUD muncher, you've never spent the day or two of regular usage that it takes to overcome that learning curve.
However, once you get used to it,
EVERYTHING I've ever done in Vista is far, far easier than XP ever was. If only because of control panel + search = awesomeness.
For anyone who missed it, this is an absolutely fantastic resource for anyone bitching and moaning about Vista - especially those of you who are a part of the vast majority of people who bitch and moan about Vista without ever having actually used it regularly on your own PC -
http://www.tweakguides.com/VA_1.html