I have the Lasermax guide rod lasers on my primary home defense pistol and primary CCW pistol. I train mostly with iron sights, but I like having the option. If I am hurt, or in a strange position (injured, laying on my back only able to use one arm or even barely able to move that arm at all), or my wife (who is a decent shot, but not as confident as me) or anyone else needs to use the firearm I like that there is a point and shoot option. I tried the lasers that attach to the rear of the grip, but I didn't like that they activated EVERY time I held the firearm. They also added bulk, which matters when CCWing. I like the internal one as it doesn't add weight, bulk, and can be turned on or off at your discretion. They also don't need to be sighted in. Of course they aren't going to be dead on at 25 yards, but for personal defense encounters they are great.
I say if you want an alternative to iron sights and have the money then get one. I haven't been disappointed.