People familiar with the matter said build 10F564 weighs in at 600MB -- roughly 20MB larger than the previous build. Developers were reportedly asked to focus on Graphics Drivers, SMB, USB, VoiceOver and VPN.
The last beta, build 10F58, was issued to developers last Tuesday. It, too, was said to be clear of issues.
The last few builds have all contained the same focus areas and enhancements, and this week's update is no different. The updates addressed issues that could cause the keyboard or trackpad to become unresponsive, and also fixed a problem that prevented some Adobe Creative Suite 3 applications from loading.
Apple first began widespread testing of Mac OS X 10.6.4 in late April. The previous update to Snow Leopard, Mac OS X 10.6.3, was released at the end of March. It included improvements for QuickTime X and OpenGL-based applications, in the form of a 437.2MB update.