A laser is not a good thing in my opinion. Ive seen too many people who use them look at the dot instead of the front sight of their gun and do nothing but promote bad handgun handling skills. A laser is not a subsititue for the front sight and should never be used that way. They tell the bad guy right where you are destroying any tactical advantage you might have. Now having said that I will say there is a tremendous psycological deterant when someone sees a red dot on their chest and it is probably enough to end any conflict (in an CCW role). They are great for when you are doing dry fire practice and really let you see how much your moving your muzzle. Other than training I don't think they should be used by LE. Just my opinion and it is only one of many.
Tried a CT unit my dad installed on a J frame and I ended up doing the opposite. I kept trying to align the dot with the front sight blade. I did not care for the system as it caused me to have to 'think' through the sight picture. Given the complication to training and the 'choice' under stress, I went with flashlight and night sights.