1) not network friendly
2) kernal hacks are easy
3) scripting hacks are easy
4) too many background processes = boggled performance
5) the knock off objectdoc actually runs worse performance wise than the apple/objectdoc versions
6) way to many notifications
7) too many unnecessary changes that make doing specific tasks harder vs making them easier.
From an administrators standpoint, notifications & making specific things harder to get too is far too aggrovating to invest in Vista.
Vista is actually the byproduct of W7. Due to SP3 for XP, microsofts delay on W7 was so far behind that they cut huge amounts from longhorn and renamed it vista and released it. They should have just delayed the release which would have made many people such as myself happier.
Edit*
Vista has due credit as being a gorgeous looking OS but looks can be decieving.
I'm bored of XP honestly. I've been using the W7 beta for quite awhile as my main OS. Haven't had nearly as many issues with it as the released version of Vista as with the W7 beta. Although it does have a few minor bugs, the major bugs aren't particular easy to manipulate. Plus Windows announced the ability to turn off IE8 in W7 so if you're not an IE8 type of user you can later install IE7 or lower to support user wants/needs.
I am a network admin myself, and we do not deploy it on our network...but that is because my company is Uber-cheap.
As to background processes, many of them can be disabled to no negative net effect, but it does reduce CPU cycles.
I just have not found Vista to be the 'boogey man' that many users claim it to be. It's more or less XP with a fancy coat of paint...and some annoying pop-up messages. But you can turn those off too.
I do not like the fact that it hangs the UO launcher, and gives the Ulitma Online is loading problem, but you can work around that by shutting off the fancy interface...thereby sending yourself back to XP essentially, or you can just perform an action that forces a desktop refresh, like changing rez.
All and all though, I give Vista a B- out of the box, but a solid A after some minor tweaking.
You are right, XP had gotten rather old...and I am looking forward to W7, although it is going to cost me a bundle to upgrade the machines I have that I want to bump up. On the upside though, the other ones get the bump to Vista, so not the worst thing in the world.