I totally believed the perception that Windows Vista was a failure. Everyone I talked to hated it, no one was buying it, I even have half a blog post written about how Microsoft is doomed because Vista failed. But then I needed a new computer and asked for advice and it turns out most people who actually use Vista like it.
Now I'm one of them. After a month of using Vista I like it just fine. It's not so much better than XP that I'd upgrade an existing computer, and there are rough edges with old applications. But in general it's a fine Windows OS.
The main improvement I appreciate is the UI. Aero, the fancy 3d/translucent thing, is a bit fluffy. But it's kind of grown on me. The font rendering is good and the new screen-optimized fonts are very readable. The best UI improvement is all the system dialogs, configuration panels, etc have been redesigned to be very understandable. I find it much easier to do some unanticipated task in the Control Panel than ever before because the UI is in readable English. Some of this UI is too clever for itself. For instance if Vista thinks you have a folder full of pictures it doesn't show standard file modified dates but tries to use EXIF tags instead, even if they don't exist. But you can disable most of the new cleverness if it is a problem and I've found I don't have to do that much.
There are a few new features I use regularly. My favourite is the new Search capability via the Windows menu. Press the Windows button, type the name of a program or document, and it launches. Just like Quicksilver or a zillion other app launchers, but this one works by default. It's tied into some search indexing system in Windows that seems to actually work too; a first for Microsoft.
The other new feature I like is User Access Control, Vista's compromise between running as Administrator and having some security. Most people hate UAC because it pops up a disruptive security dialog whenever you try to change a Control Panel setting or install some software. Me, I like the prompting, because it means there's a chance I can catch some malware before it gets installed. And it doesn't really come up in day to day work.
Where UAC causes problems is with older applications. Since Windows 2000 proper applications are supposed to use APPDATA and not write user data into the Program Files directories, but even now eight years later some apps break that rule. Those apps don't work well with UAC, and it is a practical problem for me. The worst offender was World of Warcraft; I finally gave up and installed it in some non-protected directory. The other workarounds are to run the offending app as Administrator, or turn UAC off entirely. I haven't had to do that with anything else, although the occasional auto-updater causes me some grief.
One final thing: not only did I install Vista, I installed Vista 64. I've not noticed any issues at all with the 64 bit OS except one: Explorer shell extensions have to be special 64 bit builds. Some of the apps I used to use don't have those. But I don't really like shell extensions anyway, so I haven't really missed it. Beyond that Vista 64 should use my 4 gigs of RAM a little better than a 32 bit OS, but not much better. And it has some funky address rewriting system that makes the OS a bit more secure to buffer overflow attacks.
So after a month with Vista, I like it just fine. Like I said, I wouldn't bother upgrading an old system. But if you're getting a new computer and aren't doing anything exotic with old applications, Vista should be just fine.
PS: Microsoft is doing some marketing campaign for Vista right now that seems to involve stupid "viral" deceptive crap. This blog post is entirely independent.