IIRC, Jeff Cooper studied this problem 30 years ago when the laser sights first came out. After some testing, he found that it was not as fast as a standard presentation..... the shooter looked for the dot, then moved it to the target.
The best use he found for the laser sights was for his dog to chase the dot around the living room floor.....
My own thoughts on them: in a smoky/dusty environment, the laser becomes visible, drawing a line (and hostile fire) straight back to the user. I'll just use my tritium 3-dot system, thank you.
TheGolden Rule of Tool Use: "If you don't know what you are doing, DON'T."