TransType 3.1.1 build 4611 for Mac OS X has been officially released:
see announcement.
This release includes an improved user interface, a number of bug fixes and runs on Mac OS X 10.5, 10.6, 10.7 and 10.8. This release is a free update for all TransType Pro users. It's also a free update for TransType SE users who will get all the Pro features!