There's a whole lot of negative bandwagon jumping going on with Vista.
I think too many people say that they "played with" or "looked at" Vista and then make a quick judgment followed by negative statements.
UAC (User Account Control) gets a TON of negative publicity for being too intrusive (UAC is what gives you the "do you really want to do this?" prompts).
It takes 4 clicks to turn UAC off. Takes about 10 seconds.
Don't like it? Turn it off and get on with your life. The sheer amount of negative publicity that one single security option gets - an option that is completely controllable by the end user - is evidence of the irrational piling on that the media does to Vista. Look, if you don't like UAC just turn it off. Don't whine about something that you can turn off anytime you want to.
Personally I love Vista. I have been using it since early betas and I switched all of my computers over to it before it even shipped. A few weeks ago I had to spend an entire 8 hour work day on an XP laptop and I wanted to gouge my eyes out with spoons by the end of the day. I couldn't get away from that damn XP box fast enough.
I currently have 3 laptops and awhile back I used one of them to do extensive XP Vs. Vista performance testing. I built the laptop with XP and then ran an entire battery of tests over the course of a week. Then I rebuilt the laptop with Vista, installed the exact same software as the XP build, and ran the same tests. What I noticed was that XP has a smaller memory footprint when first booted, and seemed to consume less memory with fewer applications open (under 5) than Vista did. However, Vista outperforms XP when you really start to stress it. With a lot of applications open Vista manages memory better and does a better job of seeming "snappy" even when its under heavy load. The XP laptop "felt" slow before the Vista laptop.
My wife is a prime example of the average user. She has an old Dell Latitude D600, its probably 3-4 years old. It has 1.5gb of RAM. About a year ago we put Vista on it. She said that she has seen no noticable difference in performance (and remember - this is a fairly old laptop), said all of her games play fine, says that she has an easier time connecting to public wireless access points (she would sporadically drop her connection in XP), and said simply that "likes Vista better". She's just your average Jane Doe non-techie user.
Yes, SBM is correct that it can be difficult to make a compelling case for enterprises to upgrade. Any enterprise software purchase is all about enabling your users to perform their tasks effectively and efficiently. A PC is just a tool that helps them do their job. In order to go out and buy the latest greatest tool you first need to understand what the problems with your existing tool are and how the new tools improves upon that. But just because many enterprises consider XP "good enough" certainly doesn't make Vista bad.