I have never given much thought to putting a light on my pistol, even though my Glock has the rail, and I will admit, having slipped a friend's on there once, it does look really cool, but have never given it any serious thought.
That being said, I can attest to the disorienting effect of having a SureFire light on the end of a long arm.
It was handy when searching through somebody's closet or dark rooms at night, and, I found that at night, on the side of the road, when somebody may or not be hostile, be abling to effectively blind them while you stop and frisk them is a pretty handy, non-lethal, non-violent compliance tool to have.
NRA Life Member
Big Sister: "You should be sponsored by Allen"
Me: "If you can't shoot good, at least look good walking to the firing line."
Big Sister: "Can you not afford a Pelican? Then buy an Allen gun bag."