Let's just wait for Service Pack 1
Every so often, I'll hear it said, and frequently not in jest, "let's wait until Service Pack 1 before we deploy Vista", or sometimes "Server 2008".
While it's true that Microsoft has indeed announced plans to test, and then release, Windows Vista SP1 early in 2008, I have to say that I don't find this thinking any smarter than the old "let's buy IBM" idea, based on the "Nobody Ever Got Fired For Buying IBM" principle.
Even if it were true, someone's eventually going to realise that if it's your job to specify what the IT budget gets spent on, and you say things like "we'll deploy it after Service Pack 1", you're just not acting as if you're doing your job.
Somebody, one day, will call your bluff, and say "Why? What bug is a showstopper for deploying Vista RTM, and why do you believe it's fixed by SP1? Why didn't you find that bug out while you were beta testing the operating system? Weren't you beta testing the operating system?"
And you're going to look foolish, because you don't have anything in particular to point to (UAC? That's a bit generic - you have to say what you don't like about UAC, and why you think SP1 will make it all better) in order to defend your mindless parroting of "let's wait for SP1".
For the record, there are reasons to anticipate SP1 - it adds an SSL-based VPN capability, through the SSTP, and it allows you to encrypt multiple drives using BitLocker through the UI (you can use manage-bde.wsf to encrypt multiple drives using BitLocker from the command prompt).
There are other features in SP1, and you should definitely consider whether you can use those features. But there really isn't any break-fix that makes it important for you to stop testing and planning to deploy Vista RTM while you wait for SP1.