I have it on my G19 and love it. I don't use it so much for eye level shooting, but doing a draw and shoot from the waist or around cover where you don't want to expose much of your body/head; you can just see the laser dot and shoot your target as long as it is sighted in.
I use it as a just another tool like you would a tac light, etc. Obviously a novice shooter needs to be profiecient with their firearm/sights/etc before adding a laser..
Certified Glock Armorer, GSSF Member
Glocks: G19C Port w/CT Laser
G27 w/TruGlo TFO, G21 w/CT laser
"Rather be Judged by 12 than carried by 6!"