Great for what it is - OpticsPlanet Exclusive Crimson Trace Defender Series DS-125 Universal Laser Sight

One day just for fun I squeezed of a couple hundred rounds with this attached to a glock 9mm. It stayed tight and secure. Just remember its not like a movie or video game where the projectile hits exactly where the dot appears.
I can see this being somewhat useful if you didn't have time to sight a target in or had to shoot from the hip for some random reason. Again, without pinpoint accuracy, one should aim for center mass.