I haven't used the final edition of Vista that is in everyones hands now but I still use a RC1 version at work for testing until we can afford to get a new machine with a real version actually installed. So I have some experience with it.
I find RC1 has some bugs, occasionally a temporary folder seems to fall under some sort of shared status between administrator and users on the system so you get a warning all the time. I'm sure they fixed that. Might be something I did in fiddling with it. The UAC is fine if it didn't ask a half dozen times about something doing something. I understand that was toned down after RC1. The visual interface is both good and bad.
The good is that its about bloody time they leveraged the 3D cards power...Linux distros just started working on this too and MacOS X has been doing it for years now. Its smart, I'm a sucker for shiny things, and I'm right pissed off with WinXP and Win2000 not drawing the screen properly when the CPU is busy or having to refresh icons on my desktop because in Windows explorer I clicked on the CD drive.
Its also a bit of a memory hog but I understand that has allot to do with aggressive caching of software which is fine with me. Load times on the same dual booting laptop are much better in Vista RC1 than WinXP for things like Firefox, Quicktime, and some of the other software apps that we use. No games at work so no idea how that goes over personally...I hear the initial reports were terrible but things are improving as the video and audio drivers get updated.
Judging from reports and charts...there's a performance peak where any computer with a certain set of abilities is faster in Vista than XP because of optimization for new technologies. You can patch old software to a point but I do think its good to go back and re-write stuff which they did apparently do. The charts seem to agree...anything that I've seen. On the other hand older machines are choking on it. Ultimately its the same Microsoft arrogant mega corporation attitude with a mix of occasionally doing the right thing and a dose of mismanagement tossed in there.