There's many, many things wrong with Vista, but as you say, for most people it does just what's needed of it.
Let's start with the biggest problem for me - the User Access Control - a feature that stops all operations and ask you if you're sure you know what you're doing. All you need to click is yes & you've broken you're computer, it's an utterly pointless intrusion.
Then there's the bloat - why should my dual core PC with 2gb of RAM be slower than my 5 year old Athlon PC with only 1gb of RAM.
Thirdly, the stupidly slow file copying, it sometimes takes 1/2 an hour to shift a couple of hundred megabytes of files across to my backup drive, XP will do the same job in about a minute.
I'm sure others will chip in with more when they've finished lynching Radio 2 presenters...