I know I'm a bit late with this post, but just in case you haven't heard, Windows Vista SP1 is now available for TechNet and MSDN subscribers. For TechNet subscribers, please go here: http://technet.microsoft.com/en-us/subscriptions/default.aspx. On the lower left portion of the screen, you will see a section titled "Top Subscriber Downloads". Click the file you want, log in and away you go.
I am not making a lot of fanfare around this on my blog, but this is a huge milestone for us.