There is a mixed bag on what people feel about lights and lasers around here.
A laser to some is a fail safe for target acquisition. People will say you will end up relying on something that could fail (dead battery or such)... I personally feel that in the event I see some old lady getting mugged in a parking lot... a laser on the perp from 50m could help in stopping the problem from proceeding without a word from me or having to get too close.
A light, some will say causes blindness and almost keeps the invader from knowing they're about to have there word changed if the issue doesn't cease. I think of it like this... I'll make it quite clear that a gun is trained on the perp... if he doesn't believe me... he can take a step towards me where as then I will feel my life is reasonably in danger thus giving me the right to fire... if the perp sees you have a gun, they may try to flee... thus eliminating my reasonable doubt that I'm in danger and taking away my right to teach said perp a life lesson.
Remember... you can put a value of property, but not human life... even if in your mind, the life if worthless. You can shoot if you are reasonably if fear of life threatening danger but not if they are stealing your VCR.
As Ive said... you will get mixed answers.
I like a light/laser but unfortunately... my current Glock is rail-less so I cant easily affix any light show deterrents.
Hope that helps.