I got the final Release Candidate Version of Vista Service Park 1 from an email from Microsoft.
From what I have seen and experienced there is not much Vista will do amazingly well now, still runs at the same speed, uses the same amount of memory and starts up at the same speed.
Fair enough there maybe some security things they have addressed which work away under the skin, but I certainly haven't seen anything that shouts out "Wow this is so amazing".
The final release should be available within the next week or so, but they are working through problems with compatibilities of the language packs.