All the time.
http://www.pokerhand.org/index.php?p...amp;hand=58938
One thing to remember though is that if you do you must first work out on the river, that your opponent has atleast one pot bet left. If you bet the pot on the turn and your opponent has a set, he will often call just because he is stupid, if he hasn't got much left on the river he may just call it off anyway "since he has value to call" (what a stupid statement fish use).
In fact in the games I play, I will often call the flop with a naked ace flush draw simply because if it hits, its the same as having the flush, you bet, everyone folds (because I'm a good player you see, so I always have it).
What makes the naked ace so powerful is Omaha is a game about the nuts. If I know nobody has the nuts I will always bet the pot since no-one can call. The Ace is the only way this can be achieved without actually having the best hand at the table. (apart from of course holding AAAA on a QJT98 board, although you best hope your opponent doesnt have KKKQ else he might just figure you for the rob ;-) )