Thats right, despite the many reviews posted by various websites calling for a Beta 3 Microsoft have stuck to their roadmap and gone from Beta 2 to the RC1 branch. I wonder how many RC's there will be?
Last week, on Friday, Microsoft made a branch for the RC1 Milestone build. The branch is known as 'vista_rc1' and began with build 5504.16385.vista_rc1. Don't confuse this with the RC1 winmain branch that began with the build 5420.0.winmain.060427-1900 back in April, because that branch is still pressing on and will most likely see a build number jump soon enough. By the way, I should note that 5504.16385 is effectively equal to the build 5489.0.winmain which was built the same day.
Alot of you will notice that 5504 caries a new revision numbering scheme. However, this scheme was causing problems in 5504 (ex: The Windows Sidebar wouldn't work) and was temporarily removed with build 5505.0.vista_rc1.060731-2200, but you can still expect this new revision number system to be in the next interim build released to the Technical Beta Program. I will also say that you should expect RC1 to milestone later on this month and at least one interim build from the vista_rc1 branch should be released to the Windows Vista Technical Beta Program between now and that milestone.