I was advised by a local police instructor who works in a gun store to stay away from lasers for various theoretical reasons. However, at my concealed carry class, the instructor, who still uses his favorite model 1911s at the range, said he has laser sights on his DA-only SD handguns. He emphasized two relevant and related things: range shooting and self defense are two entirely different things; and in a close range SD situation with a rapidly approaching opponent, the short time available to draw and fire and the close distance to the large moving body mass make a sight picture irrelevant.
On the strength of that I bought the laser and have been practicing with it. No regrets.
I am "programming" myself for an entirely different reaction from my years of range experience. The quick shots at a big blank target--forget groups in the ten-ring--are part of this, and another is to avoid single action shooting. With my 642, that's a non-issue, but it has to carry over to other weapons.
I think the laser is invaluable.