Places like Firestone, Goodyear, Tires Plus and all those chain stores are really hit and miss. A basic alignment is pretty hard to f up but it happens all the time. The chain stores sometimes have good technicians and bad ones so unless you know a certain guy at a certain store, I'd pass just to avoid the potential hassle of their screw up.

In Roswell (well, Sandy Springs) I'd trust DeKalb Tire on Roswell Rd over a national chain joint. If you cant make it to Gran Turismo (add my vote of confidence to that place), DeKalb will probably do a good honest job for you.