If you're training with a new firearm, or are new to shooting in general, a laser can be invaluable for dry fire situations. Even turning it on for the first shot, using your sights, then turning it off for the duration can be a great way to get used to new sights or shooting in general.
Lasers also pose a problem in law enforcement. Mainly on drug raids or when serving a warrant. If you bust down the door and there's a few gentlemen with the business ends of their shotguns aimed at you...and you ALL have lasers....which one is yours? That half a second or several seconds could cost you your life.
I could understand how a laser would help if you were trying to hip shot...but seriously...if you're counting on a hip shot, you might as well not even bother. 'Cause you're most likely not gonna make it out of the situation.
Once I get my funds in order I fully intend to buy some night sights for my PT145, and possibly a tactical light. The bright shock of a Tactical light could give you that half a second edge over someone who is trying to take your life. That, and you don't have to bother pulling a flashlight out of your pocket. (or off your belt)
All the police officers in the town I live in carry the Sig P229. They come standard with the Crimson Trace grips, and almost every single one of the guys has removed them. My step-dad was the Arms Instructor for the department here for 22 years. When he was still a Cop, he had the Chief sign off to let everyone carry their own pistol if they chose to do so...most did. His parting gift before getting disability (hearing loss...who woulda thunk it?) was to find a reliable standard issue sidearm for the department. I believe that was the P226. (That was in 2000)