Having used CTC grips on some of my guns in the past, I will second some things others have said, and add a couple more.
They are good dry fire aids (and bear in mind, with poor trigger control, the bullet DOES NOT go where the dot is, so dry fire is essential);
They are useful in low light, and in situations where conventional sight alignment would pose challenges;
but, also already said:
I am faster and more accurate using irons.
Not yet said:
Lasers are very useful for the bifocal crowd. My mother has a very hard time focusing on the front sight and still seeing the target - the dot lets her focus on one plane;
Lasers allow the defender to focus on the threat, rather than the front sight, enabling a better scan.
Still, in my case, I gave my last laser sighted gun to my parents.