I have many, and have successfully used them zero times.
Lights, on the other hand, are very useful. Every time i've used one, someone on the other team has shot me. A 100% success rate.
Also, it seems to me that red lasers are only good for indoor CQB/night games, and green lasers are only good for outdoor day games.
I have an ally NGAL on my 416, which is really nice despite being really for decoration.
My SD has a Surefire clone on it.