I posted, P #10:As a further check I logged-in to Ubuntu 2d, and Unity 2D does the same FullScreen trick of hiding the top line behind the title bar.Edit: I have just logged out & in to check that both Unity and Gnome Classic in 11.10 behave the same way. It is limited to an Ubuntu log-in, in Gnome Classic, it does not occur and grahammechanical's description applies.
BTW File Manager Windows also behave in the same way, when Clicked to FullScreen.
With Gnome Classic, the top bar is a 'normal' Gnome Panel, that can be edited or removed with the Alt+Right-Click drop-down menu, or easily have Icons added, which the Unity top bar can not.
Perhaps this is to do with the Global Menu, which Gnome Classic does not have.
Personally I am not bothered by this, as my Mouse works as I would expect.