Vista SP1 RTM was 2/4/08. All your users can get it in mid-March via Windows Update and the Microsoft Download Center. IT Pros can get it today if they are TechNet subscribers. Just log on to your TN subscription home page and check the "Top Subscriber Downloads" section.
Basta. Content thee.
Just signed up for technet last week with a new subscription and I'm happy to already have Vista SP1 downloaded and installed on a testing PC. Anxiously waiting for Server 2008 with Hyper-V to be available for eval!!!