Other things of note:
Mac App Store App has also been updated today
After the update it asked again for my iCloud Account. Skipped it and then everything was ok.
Clover, GA-Z77X-UD5H, GTX 650
Current UniBeast works with the updated 10.9.1 App.
Wow, what timing. After reading page after page of GTX 780 Rev.B compatibility issues, I've very curious to see if this update fixes the problem. If anyone has that card, please let us know if there is any improvements.