Overwatch is pretty deadly... however, don't forget the -20 to BS when setting an overwatch.  Going full auto would buy that off, but it's not as deadly as simply firing on full auto on your own turn.<br/><br/>The advantage of Overwatch, however, is of course that you can act during another person's action... (like when they're moving through the area you're covering...)<br/><br/>If Darius had had overwatch on that grate that the mutant tossed the krag grenade at the Sentinel from, he'd probably have killed the mutant before he could throw it... although it would have reduced Darius's hits from 7 to 5...  But of course he didn't... he didn't see the mutant, and therefore could only act after the fact.  (lucky that the mutant rolled poorly on the krak grenade damage.