I had this issue in the previous beta and had hoped it would be resolved, but am still seeing this with the latest release. Though, at least now it seems the drop-down bug has been fixed (previously, I wasn't able to change any of the options in the settings because none of the drop-downs would drop-down when clicked).
Whenever I enable full screen mode (either through the Options->Full Screen toggle - or by using the Cmd-F option), it goes full screen, however there is nothing displayed. Just a black screen. The game is still running, as I can hear game actions and music - and my cursor seems to change to the appropriate style when over things - it is as if the game is running, except all graphics - except for the cursor - are 100% transparent in front of a black background.
Specs:
Mac Pro 2013 (nMP)
AMD Firepro D700 (2x)
16GB RAM
2 displays - each running 2560x1440