I think Vista is great, and mostly undeserving of the bad rap it gets. And this comes from a decidedly "anti-Microsoft" geek who has run Linux
for 12 years now.
Now that it has had time to mature, and Vista-compatible drivers and software are the norm, the only real issue I have with Vista is its attempt at "greater security." IMO this is its biggest problem, and of dubious value. How many of you blindly click OK at a UAC escalation prompt without any idea of what it's doing? Kinda defeats the purpose, but that's the inevitable result -- users are left with the decision to click OK if they want something to work, so they don't have much choice, and then after awhile clicking OK becomes a reflex action to them. I've seen that sort of user complacency enough in my 20+ years in the software development and engineering field -- if you make something a nuisance, users will ignore it or work around it.
The key to a positive Vista experience is to disable UAC immediately after installation (NOT later after lots of apps are installed) and make sure your user account has Admin privileges. At this point things are no less secure than XP was, likely more so due to some architectural changes in Vista that improves security a bit under the covers. As long as users are security conscious and aware of sites they're visiting, their downloads, and the e-mail attachments they open, they should have no issues. Particularly if they run an up-to-date AV and anti-spyware toolset. This alone would alleviate most of the Vista headaches people run into.
I have Vista running on 3 of my PC's and have zero issues with any of them, but I configured Vista properly from the get-go.