They can have my XP when they can pry it from my cold dead hands...lol...
Honestly, I have had no problems with XP, other than from crapware loaded onto it by idiots. I have heard about countless problems and compatibility issues with Vista, and from what I hear, 7 won't be much better. Then there's the annoyance with having to approve and re approve any changes to settings. Plus there's the issues with DRM, Trusted Computing, and the like that I would very much like to avoid. Finally, why should I shell out thousands to upgrade PCs that work quite well already?
I'll use XP until they won't let me validate the keys any longer, then I'll upgrade to Ubuntu.