Our guy, Dieter, (about two years old, rescued at about one year old) LOVES tug. He also has some fear aggression issues while on leash. We've been to a behaviorist who told us that playing tug is OK, as long as he doesn't growl when doing it. Well, since we all know boxers are soooo vocal, Dieter is always growling during play, especially tug. So, we're working on training him not to growl during tug, which is working out OK. But, my point is, we have a somewhat aggressive dog and were told tug is OK, with boundaries. Of course, we play by the rules and the game stops on our command, when he growls, or if his teeth accidentally touch our skin. We've also trained him that if the toy gets near our face (we'll pull it up close to our face) he lets go immediately.
We still enjoy tons of fun tug time and it's a great way to exercise our guy when we can't get out to play (rain, snow, cold, etc.).
As long as you play by your rules, I think tug is GREAT!
BTW, I wouldn't recommend tug play for every aggressive dog -- I'm only speaking in our particular case with Dieter, since our behaviorist determined he's not a dominance-seeking dog.