Most notably, Apple has included a new round of "Bluetooth compatibility and stability fixes" in the latest beta, labeled Mac OS X 10.5.7 build 9J56, according to people familiar with the software.
A number of recent Mac mini purchasers have complained about intermittent Bluetooth connection problems (1, 2) on their new systems, though similar problems are believed to be plaguing a variety of Macs, with one AppleInsider forum member recently noting that the issue extends back to his first-generation 13-inch MacBook.
Another fix in the latest build targets an issue with Personal File Sharing and AFP volumes not being properly recognized as Time Machine shares. However, the other three fixes were relatively minor, two of which add once-missing descriptive information to certain crash logs.
In total, Mac OS X 10.5.7 stands to deliver over 110 individual code-corrections spanning more than two dozen areas of the system. Earlier this month, Apple added Help Viewer to the list of key software components where beta testers should focus their testing efforts.
Though its believed that Mac OS X 10.5.7 remains close to release, Apple still notes that the software is incompatible with the public beta of Safari 4 — the OS update's lone known issue.