Vista is the best OS microsoft have ever made. There are a couple of problems, but then again, which OS doesn't have them?
The big ones though are that it is a RAM whore. I started using vista with 2GB of RAM with Vista ultimate and on the side bar i put the CPU+RAM monitor, showing the usage of it. When idle it was using 50% of my RAM, thats a gig just for doing nothing!! And that was without aero or dreamscene or any other vista extras or ultimate extras.
The other one is that for fiddly stuff, like changeing the loading screen, it wasn't fiddly on XP or any OS prior to XP, but on vista it's security message after security message, but thats only for the fiddly stuff. For the common stuff like organising files or using the start menu it is brilliant, so much easier than any other OS on the market or any that have been on the market