I agree with Allen for the most part.
In my company I test a lot, also Vista and 2008.
I switched to Vista x64 on my home PC 6 months ago, not becaus I wanted to but to force myself using Vista. It's like a fungus, it grows on you.

Eventually I got to like it, so much I decided to install it on my work laptop. Most of my kix scripts work without change, just take WOW and (like Allen said) File System Object into account. But every new OS has those type of changes. 98 scripts didn't work properly in all things on 2000 either.

Anyway I installed McAfee 1 week ago and Vista crashed. Then I decided to switch back to XP x64 but within a week I reinstalled with Vista x64 (with Symantec x64 now) and I couln't be happier.

On a side note, we have a couple of 2008 File servers and Tools servers into production now and they are running great also, big change comming soon is switching to a 2008 Domain... I'm holding my breath \:\)

One thing I do believe is awesome about Vista/2008 is WDS deployment, I'm our company's RIS guru and used that for many years, I even deploy linux and use it to boot Acronis to image PC's. But WDS has so many NEEDED extra options that I'm totally in love with it \:\)