The release of Mac OS 10.6.3 moves closer as Apple has begun widespread testing of build 10D522. According to AppleInsider, this update focuses on stability and core components like AppKit, CoreMedia, Desktop Services, FileSync, Fonts, HIToolbox and more. The current build is 665.7MB in size.
Reports indicate that nearly 60 crash-happy bugs have been squashed across more than 90 components with this update, like printing issues with iCal, Mail and PhotoBooth (fortunately I haven't experienced those). Additionally, 10.6.3 includes native support for the Magic Mouse.
Apple began limited testing in December, and has released several builds since. Now that testing has become more widespread and the fixes increase, we move closer to release.