I had a lasermax in my G21 for awhile. I was not a fan of it. I will add that it operated flawlessly and there was no problem with accuracy. I read the argument in an earlier post about it not be adjustable and the difference between two people shooting the same gun. First off this is a combat laser, it's not intended for bench shooting or shooting for accuracy. In a combat situation the goal is to be able to get bullets on target fast. Anything in center mass if more than acceptable. With that said most shootings occur very close and very fast, often no time to fumble with a laser as it takes time away from getting off that first shot. As for the lasers range, it really doesn't matter because a handgun for self defense is very limited at longer ranges, especially the heavy slow 45acp. As for two people shooting the same gun differently it is usually due to sight alignment or poor trigger control, the gun shoots the same, people don't.
As for my reasons for not liking the lasermax, it slowed me down if I tried to use it. When doing close quarter stuff where you have to draw and fire quickly you don't have time to fumble with an activation switch. Better off to train and shoot often and rely on the sights in my opinion. Anything less than 10 yards I don't conciously even look at my sights. This is a result from shooting thousands of rounds through the same gun, muscle memory and feel just takes over.
The only plus side I see to a laser is for intimidation. When a person sees a red dot on their chest it makes them stop and think for a second.