I've not seen enough in action or tried one to be able to intellegently make up my mind. The biggest potential problems I see are relying on them instead of a proper sight picture, and them either failing or becoming knocked out of alignment. As a range officer for department qualifications I watched one of our retired officers use a laser sighted 229/.357 Sig at night. He used the laser instaed of his flashlight, so didnt know if he would be able to id the target or not. I can see some good, but the POSSIBILITY for bad also. If you rely on them and need them in bright daylight, you might be watching for the dot and not paying attention to what is going on. I dont rely on night sights either, for what it's worth.
I've been handgunning since my US Navy days in the early 1970s, and full time LEO since 1975. I'm a FBI trained, state APOST certified firearms instructor since 1983, and do more shooting than the average gun owner and police officer. In my opinion, less is better, but there is always room for improvement, as long as the improvement dosent pose more liabilities than benefits.
As an aside, I shot alongside the above mentioned retired officer during rifle quals, which is only 10 rounds at 50 yards. He had a Bushy in .223 with lights, a laser and a HOLO sight. I outshot him with an iron sighted Marlin 9MM camp rifle.
I see a lot of shooters buying add-ons hoping to make up for poor shooting habits and seeing the latest piece of equipment as a fix for poor scores or large groups. A new $2000 custom 1911 will "surely" fix their poor scores and large groups caused from trying to "wish" and"spend" themselves into a class A shooter's position. These are very much like the golfer who is convinced the newest set of clubs will make up for his failure to practice or get professional help from a local pro.
As I see it now, and have for 30+ years, you can't spend your way out of poor shooting habits and failure to praqctice.
Please, no flames, there is no intent here to rain on the laser parade. This is just from 35 years of handgunning/policing/shooting/instructing, and what I've observed first hand.