I'll take a good flashlight over a laser everytime. Lasers are great aids, but the do not identify a target in the dark. For daylight shooting nothing beats practice, practice, practice.
If the laser you are looking at is cheaper the most of SureFires flashlights, I wouldn't bet my life on it. And this goes for rifle, shotgun or pistol!
I like the Crimson Trace Lasergrips. Although I like normal sighting the most, I practice with the laser and feel comfortable with both methods of sighting.