My problem with this thing is that if you shoot someone, you stop and stun him for a very short period of time. When facing archers you regain your ability to move before they can shoot again, so its not impossible to dodge. A repeating crossbow however would make it very easy to hit an enemy with all your bolts.
You hit once, he staggers, then you just shoot the rest of your clip, while he just stands there staggering and probably crying.
It doesn't matter if it has little stopping power if you can get 6 bolts in.