This must be the maintenance update that has been the longest in testing in the history of OS X! Five days after releasing build 12D74 from OS X 10.8.3, Apple today made available another version for testing, that of build 12D76 by our accounts, at 12. The focus remains the same as before (AirPlay, AirPort, Game Center, graphics drivers and Safari) and the new version arrives without known problems. Who live, see update!
(tip from Renato Molinaro)