I'm with AK103K. In my experience, many of the people who are interested in lasers are newer shooters who see them as a fix for any issues they might be having with their shooting skills. But they're not a fix for poor shooting, they're simply a tool. They're a tool that I find annoying and distracting, but there are plenty of skilled shooters who find them helpful, so I'm not going to completely dismiss them; but you should definitely try one before spending a few hundred dollars on something you might hate.
Also, is this laser for a home-defense gun or a carry gun? If it's for a carry gun, I highly recommend using one of the passively-activated lasers like Crimson Trace makes. That way you don't add a button press to your draw. I'm a fan of simplicity, and in a concealed-carry situation a quick, simple, smooth draw is extremely important. Adding an extra button press to that draw is a bad idea in my opinon.