The Windows team stepped up a gear and have released SP1 RC (Release Candidate) Refresh 2 today. In the past this probably would of been called RC3.
Microsoft said this release would reach just 15,000 official beta testers who can download it through Windows Update or as a stand alone file. As with previous builds, the Service Pack requires an RTM version of Vista without earlier SP1 updates applied.
Service Pack 1 is expected to be made available in the middle of next month.