I have had a laser (LaserLyte sights on a G19) on my carry weapon about 3 years now...out of about 36 years of carry. I have not had the need to use it (or my weapon for that matter) in that time, but there were a few times in the past I would have loved to have it. It is a good training tool to highlight shakiness, jerking when firing and for those who practice train fire.
I would never try to engage it if I were drawing in defense unless I was shooting from cover...but there have been times in my past when I would have really liked to be able to shoot aimed shots from cover without sticking my whole head out from the cover...that is why I wouldn't be without one again if I can help it.
JMO...YMMV
I had to add something after reading a post above...as far as it giving away your position, this would only be an issue at night and if you haven't fired...once you fire, the muzzle flash is far more visible than the laser dot that can't be seen unless you shine it in their eye. It's one of those arguments against I hear all the time that makes me just shake my head.
Gun Control: The [liberal] theory that a woman found dead in an alley, raped and strangled with her panty hose, is somehow morally superior to a woman explaining to police how her attacker got that fatal bullet wound...L. Neil Smith