Vista is what drove me to Mac OS, Windows 7 does not seem like much of an improvement in my limited testing. I hated the fact that Microsoft would just move everything around for no good reason, so I had to relearn to do everything I could do in XP. I managed with Dos v3.3 -> XP.
I also used Vista for 3 years, and recently moved to 7. It boots much quicker and uses less resources on a consistent basis.
Of course I realize that the plural of anecdote is not data but I haven't heard anyone contradict what I said.