Currently my wife and I fly on the airlines about 6 or 7 times a year, hardly what one could term frequent Flyers. To be honest we avoid airline travel as much as possible. However, when forced to travel on the airlines due to time restrictions we do everything possible to be seated on the exit row.
Part of the reason is indeed the extra leg room, I'm 6 feet 5 inches and my wife is just under 6 feet tall, we like the room. However, the primary reason is for our safety. I am a semi-retired (looking for work) corporate/government pilot and my wife attended Flight Safety International Flight Attendant Training School and has served as a Corporate Flight Attendant.
We have opened emergency over-wing exits, we know how heavy they are, we know not to leave the exit window laying in the seat next to the exit, as some carriers still require. In fact I was nearly removed from a flight because I told a lady sitting next to the exit window that she was not to leave the window laying inside, as instructed, but to throw the thing out the exit hole and don't let go of it. Well, the FA overheard me and the fight was on, we finally agreed not to agree and carried on.
No, the primary reason for our desire to be placed in the window exit row is because we have no desire to die because some incompetent fool can't figure out how it really works, then takes too long to open it and then is to damn fat to fit through it.
So hell yes, have the dead-heading crews sit in the exit rows, if I can't at least I know for sure that there is someone sitting there that does know how to operate the exit. Or even better, when not to open the exit.