Apple has accelerated the Mac OS X 10.5.5 seeding with build 9F17 delivered to developers last night. The latest build still lists no known issues and provides fixes for iCal, Mail Sync, Back to My Mac and Core Animation.
Apple Accelerates Mac OS X 10.5.5 Seeding (9F17)
Apple Accelerates Mac OS X 10.5.5 Seeding (9F17)