I don't see a down side.. Shrunk my groups 50% at 10 yards.. since I"m a little far sighted I can't focus on the front sight so everything I"m seeing at is a bit of a blur but with the laser I focus on the target.. Great piece of gear IMHO
They are not accurate at longer distances. They are like a laser POINTER telling every one in the room or woods where you are and that you have a gun and who you consider a threat. You can't see them on a wet or glassy surface or on water. It's a battery, electronic, complicated doo dad thing to quit when you need it most.
Those are the down side as I see them.