It's a good training aid. It helps to see how much you move the gun during dry fire drills. It is also helpful in learning instinct shooting. In my mind they have limited use in actual self defense. If you are new to handguns I will give you this advise. Don't learn to depend on something with batteries, and circuits to defend your life! Learn to shoot properly, and use the laser only as an aid to shooting.
Cheapshooter's rules of gun ownership #1: NEVER SELL OR TRADE ANYTHING!