I used the ATM on my Fantasy cruise - $5 a pop in addition to whatever your bank charges. And yes, they DO run out.
On the Glory it wasn't inside the casino, but somewhere else on board.
Carnival Elation March 11
Carnival Imagination Sept 07
Carniival Sensation Dec 06
RCI Sovereign of the Seas Sept 06
Carnival Miracle Sept 05
Carnival Glory Sept 04
Carnival Fantasy Jan 04