10.6.3 Update Breaking SMB Mounted Volume Write Access for Many

If you need to write to a mounted volume over SMB, you might want to hold off on updating to OS X 10.6.3 if you haven't done so already: Apple support forum users are reporting major problems in multiple threads that SMB is borked.
Reader Eric Dube writes:
[T:]here seems to be a systemic issue with the [...:]