I got a triple boot going. Vista, XP, and Ubuntu. Vista and XP aren't as bad as people make it out to be. Vista is in the same phase that XP was when it started. I remember a lot of people complaining because 128 mb of ram wouldn't cut it on XP. Now, that's not even an issue anymore. The problems with Vista will hopefully be solved with the release of the service packs. XP is by far the easiest OS to deal with. A lot of people complain about it, but these same people do very little to try to take care of that environment. They surf sites that are riddle with ad-ware then complain that XP gave them ad-ware. No, it didn't!
Ubuntu for me is just something to play around with. I rarely use it. It's great, but a lot of the games I want to play, I have to do some crazy things just to get them running. When you screw up, you can screw up pretty big and things can get extremely technical. Ubuntu vanilla is really unimpressive, but once you get things running like compiz, it can be extremely flashy. I basically use Linux to compile things that Windows would not be able to do.