I've used most of Microsoft's OS's since DOS 2.0. I did manage to miss ME and 2000.
I currently own 4 PC's- a desktop CAD workstation with XP, my home machine with W7, and my workstation laptop with Vista Pro. Some days I manage to use all 3 of these. I also have a small travel laptop with W7. I have no real problems with any of these 3 versions of the OS. In general Vista boots much slower than the others (I helped that a lot by installing an SSD in that machine), and I like the look of 7 the best. Each of the 3 versions has a different implementation of "my documents", and I like that part best on XP. Overall I suppose I like 7 the best, but nor for any overwhelming reason.