Windows 8 has hit build 8006 and was compiled on May 13 at 6:55PM. The built number passed the magical 8000 mark somewhere between April 29 and May 12. If people remember the Windows 7 beta, with Windows 7 beta being build 7000 and release candidate (RC) being build 7100, RTM had the build number of 7600.
Microsoft might not follow the same build number milestones as Windows 7 did, but we know that beta builds of Windows 8 are having the same success that Windows 7 received. This can only be a good thing and lets hope Windows 8 continues on its success being closed, beta doors.