The first beta of OS X Mountain Lion 10.8.3 has been released to registered Mac developers. OS X 10.8.3 beta 1 is identified as build 12D32 and focuses on AirPlay, AirPort (wireless), Game Center, and graphics drivers, though it’s not yet clear if the intention is for bug fixing, feature enhancements, or a bit of both.
Installing the release must be done through a new OS X Software Update Seed Configuration Utility, which is a separate download available to developers. The release notes indicate several known bugs with the first beta build.
Those registered with the Mac Developer program can download the 10.8.3 beta and the required Seed Configuration Utility directly from Apple’s Developer Center. Everyone else will have to wait until a public release is available sometime in the future