It annoys me when people say 'those who complain about Vista have never used it' or 'those who complain have crap computers'.
I've had Vista installed on this system of mine for a few weeks now on a 2 year old system and I can openly and whole-heartedly say it's a horrible operating system. It just does so many things backwards, and to completely new PC users I don't see how it can be any more intuitive than XP, less so I think.
FYI, my rig is a Core2Duo (E6400 oc'd to 2.8GHz) with 2GB of RAM, a 7600GT (old card by today's standards but still a great budget card nonetheless). Why should I have to upgrade my computer to play games that run badly on Vista which ran perfectly on XP? I'm talking about most Source games here. 700-800MB of memory used on an idle desktop within just a week of running Vista, that's poor. It's an unnecessary resource hog.
As much as I'll slag Vista off, it's hardware detection and support is brilliant, but that's about all it has going for it.