I have three sets of Crimson Trace Laser Grips, one set on a Smith and Wesson 638 Bodyguard, one set on a Sig 239 and one set on a Glock 34.
I think they are a useful tool although I hate the fact they can give your position away and I do not like the fact that the Glock laser does not have an on/off switch where the other two do where in a tactical situation you could turn it off if you did not want to give your position away where on the Glock if you accidently grip it hard enough the laser will deploy.
I have two schools of thoughts on sighting in the laser and have had fun trying out each. One method I set the laser just over the front sight so when if you bother to line up the rear and the front sight the red dot is just over the front sight and it is only dead on where the laser intersects the path of the bullet at one point. For the close range work of laser work this is fine however at the longer ranges the path of the laser and the bullet diverge significantly and you can see a red dot for a fair distance at night, however I have not done tests to see how far you can see the laser at night and how far off your bullet impact would be using the laser.
The other method I have used is to install the laser and shoot at the range, confirm it is shooting a little low and to the right and just leave it alone. The school of thought here is that an inch low and an inch to the right at close range will not really matter at close range in a self defense situation with the adrenalin flowing and shooting dead center mass. The other thought is no matter how far at night, if you can see the laser it would probably be shooting close to an inch low and an inch right even with the bullet trajectory, as opposed to way off where you set the laser to coincide with your bullet trajectory at just one point at close range. Once again I have not done night tests on this to see how far I could see the laser and shooting to see if this is true.
For the close range shooting of the laser in self defense work I think either method would work just fine.
I hate white light at night you just gave the enemy a perfect target to shoot at with you behind it,,,but in a civilian world what they never mention about lasers or night sights is that you should identify your target before you fire and with the target illuminated and unfortunately with light spill to a certain extent you too depending on how you place the flashlight,,,in some cases just plain old iron sights will work just fine.