My experience pretty much mirrors what's already been said. Aging eyes show now mercy.
I have a FF III on my Glock 40, a Bushnell on my 617 and another FF III on my 629 PC. 2-3 inch groups are the norm and probably a little better with the 617.
I probably wouldn't take a shot past 75 yards with a dot but that speaks more about my level of skill than anything wrong with the dots or the guns.
All of my shooting with them has been benched or sitting. I tried them/use them as they are lighter than a scope and don't add as much to the gun.
John