I rarely use AA even if my rig easily handles the game.
My general setup in almost every game:
V-Sync: Off (unless there's bad tearing)
Shadows: High (or one setting lower than maximum. Generally looks the same but gives a huge performance boost).
Bloom: On (game dependent, some games go a little nuts with bloom)
I find nearly every game I play looks and runs better with these settings.
AMD Radeon HD 6970