PAX hit all the right notes.
CT Laser grips are ideal for use with J-frame revolvers IME. Obviously they can work well with semiauto pistols for many folks, too.
Since the axis of the laser is significantly different from the axis of the iron sights for very near targets, it's a good idea to sight the laser in for a specific, and typically an intermediate-range, distance. (I use 7 yards.) At that distance, the target POA with the iron sights and the laser POA should coincide. If the shooting distance at which you end up needing them is MUCH shorter or longer, treat the laser dot as "approximate only".
IMNSHO, laser sights address a genuine need for ability to hit in poor or low light, for ability to hit when circumstances are such that aligning your eye with the iron sights might more prominently expose your own head to gunfire, and for ability to hit from disadvantageous positions such as being flat on your back or off balance. They're best NOT conceived of as a proper or routine substitute for use of the iron sights, and IMNSHO are a rather poor "training aid" for new shooters (I'm sure Crimson Trace would argue with that). They serve best as a tactical option for particular circumstances, but in those circumstances they can play a genuinely-useful roll.