Microsoft has put the Release Candidate of Vista SP1 into the hand of about 15,000 testers recently. I’ve got my invitation to give it a go, but won’t be able to for a bit as I’m in a heavy work period and don’t want to take a risk just now. But if you’re looking to find out how things are working, you might want to follow Colin Walker on Random Elements. He blogs some of the best info on betas and new releases out there. He already has an Initial report up on Vista SP1 RC.