Fullscreen (Windowed unchecked) isn't working correctly on my Retina Macbook Pro. All resolutions are broken, including the lowest, 1440x900 and the Retina native resolution. The symptom is that only the bottom-left corner of the screen is shown. Changing the resolution changes how much is displayed (can get up to about 3/4 of the UI), but it's never a useful amount of the screen.
Rummaging around the Unity developer site, it appears to be this issue: http://forum.unity3d.com/threads/mac-os-fullscreen-problem-retina-display.217858/
Windowed mode works fine.