I'm FReeping from a Vista Beta 2 system right now. Easy as pie to set up, and I just configured it to my liking. On the machine beside me I've just installed Vista Beta 2 Longhorn Server. They're both running fine.
So far, if you like Win XP, Vista will be a snap. Right now I'm still evaluating.
For the Vista Client::
Advantages:
Easy to set up
Easy to configure
Pretty screens, icons, wallpapers, etc. Pretty environment
Lots of new games
IE7 works pretty good, but is different
Disadvantages:
Didn't have my drivers for my 3com 905c network adapter
Didn't have the drivers for my RealTek audio card
(both easily loaded from XP-era media)
Will take some getting used to
Lots of new features to learn
For the Vista Server::
Advantages:
Plain non-nonsense desktop
Easy configurator and role installer (sets up DNS, DHCP, etc)
Works with both IPV4 and IPV6
Disadvantages:
Same as Client above
Massive changes to Active Directory (only just started reviewing)
Many more features that I'll have to learn (also an advantage!)
Didn't have mythe drivers for my 3com 905c network adapter
Plain non-nonsense desktop