I started using VISTA after my previous PC died. At first, there was a problem with hardware compatibility, because drivers were not available. That problem went away after a few months. The next biggest problem was software incompatibility. Some software companies decided they would not support VISTA, and made no attempt to correct malfunctions caused by the programs making use of unsupported "features" of the old XP system. The third issue was the heavy handed "protection" that MicroSoft decided to cram down the throat of the users. Far to many security related pop up boxes. Most of the security stuff could be bypassed with a bit of snooping and setting some parameters in the system.
VISTA does have some very good features that are user oriented, but the aggravation that most people have with the system counteracts the benefits. It has a steeper learning curve than most people are comfortable with. At first I hated it, but after a couple of years I would not want to go back to XP.
I will take a wait and see approach to the new operating system they are developing. It normally takes about a year after release to the public before MicroSoft gets the worst of the bugs out.