Apple has released the first beta of OS X 10.8.3 to its network of developers. Available through their Developer portal, this early build lists specific areas of testing. These areas (which are typically the aspects of the OS which have been updated) include AirPlay, AirPort, Game Center, and Graphics Drivers.
The updates to the graphics drivers on various Macs seems to be causing some issues, as Apple lists various drawing issues as potential problems. For example, using the Command+Tab shortcut to switch between programs may result in icons being improperly rendered in black, as if they are a silhouette. Other than that, Apple doesn’t list any other major issues with the build. Developers are, as always, advised to install the update on a test machine so as to avoid any potential problems or bugs that would interfere with their work.