Well, I got the ArmaLaser installed, and it has some pros and cons. For one, it allows me to consistently hit a 8.5"x11" sheet of paper at 15 yards (which I can barely do at five yards without the laser). It also adds nothing to the dimensions of the gun, just makes the shape a little more "blocky." Finally, it doesn't change the way you grip the gun at all (the Crimson Trace on the Kel-Tec does put a small button just under the finger guard).
On the bad side, your finger has to go inside the trigger guard to activate the laser. That is far from ideal.
Overall, I think it's a great addition to an excellent carry piece. Also, the ArmaLaser came with a DeSantis Nemesis pocket holster, which really makes the whole thing disappear in big pockets and look like a small book in somewhat tight pockets.
Anyway, here are a couple pictures.
This last one is comparing the widths of the Kel-Tec with a Taurus 85 (5 shot J-frame).