Looking at Vista from a purley objective view, having run both RC1 and RC2 (even though i'm registered as a beta tester, i still had to grab RC2 through a torrent network since they decided to open downloads for like a day). Vista final I can't expect to be much different.
The UI is very nice, Aero looks good. One of the main gripes about Windows XP was that they stole the design from Tellytubbies. It seems to run well provided one has relatively modern hardware, older hardware just turns it off.
Its user management is nice for a novice user, by asking a crapload of questions and locking administrator rights out most of the time, security is will generally improve as programs will not have full access to the system as easilly. However, for an experianced user, it might be wise to turn it off.
One thing I noticed running Vista is it hogs ram, OSX is much like this as well. From what I see though, it appears much of it is used as cache, so just like linux generally runs at its best after some libraries have been loaded, Vista takes advantage of this as well.
I hate one thing about Vista more then anything else. It has like 8 different flavors. I can understand server, regular (professional in most cases), and maybe something like a media center edition, but to have like 8 flavors, bullshit. I'm not the typical "I hate Microsoft" person, but this is REALLY agressive marketing. Perhaps Microsoft is trying to become as insane as Apple now with Vista.
Overall, I expect many people will use Vista, gaming will initially suffer from the new DirectX and all the eyecandy, but for general use, the OS is looking like a needed improvement to XP.
Driver support needs some improvement, especially for laptops, but its not bad right now. I'll give it a year for everything to be good.
Myself, I cannot see myself using Vista, as I feel in most uses it is inferior to Linux. However, for someone not as knowledged as I am, ease of installation and OEM support is not there for linux yet. My hope is that in a year or two, distros like Fedora will improve to surpass Windows in security, driver support, and ease of use. Myself, I develop with gentoo from time to time, which is why I have such a shift towards free operating systems. The times are changing, just as web content has become more open, I believe users will become alienated with Microsoft's aggressive marketing and this slow wheel that has been GNU/Linux, will pick up and soar in popularity. Indeed, Microsoft has lost a great deal of support due to the spyware/virii issue.
In the short-term, Vista should be a sucess. In the long-term, I think Microsoft is going to have to be more competitive.