This may be intentional, but I think its a step backwards in functionality.
Old behavior: In 1.2, while playing in fullscreen mode on a Mac, hitting f11 will use my 3rd quckslot item, and f12 will access my special abilities. All function keys work this way. In windowed mode, however, the OS keybindings take precedence.
New behavior: In 1.3, while playing in fullscreen mode, hitting f11 shows my desktop, and f12 shows dashboard, despite both items having tooltips that say otherwise. Other function keys have the same problem if bound to something else in the System Preferences > Keyboard > Shortcuts pane.
I think the game should take precedence for function key input instead of the OS shortcuts that you probably won't use while playing a game in fullscreen mode. If the change is intentional behavior, then the tooltips shouldn't show hot keys that don't work. OS keybindings should take precedence over function keys only in windowed mode, as they did in 1.2.