Lasers are useful in a very narrow set of circumstances.  Hostage Rescue is one possible example.

When you use a laser, you must assume that you have given away your position, and that the beam can be followed right back to you.  Unless you have overwhelming firepower superiority and control of the perimeter, this is usually a bad idea.  Plus, most lasers cannot be seen well, or at all, in the day time.

IMO, it is far more important to use a quality optic and have a weapon light that can be activated on a momentary switch.

-Troy