Well, I do feel very judgmental today. I /might/ go ahead and shoot one if it was laying around, just to see.
Hadn't even thought of the gangsta angle. That's probably part of what rubs me the wrong way.
I've shot rifles in rollover prone, where you roll the rifle horizontal. It works fine for shooting under low cover and so on. I'm not anti-technology or anti-advancement at all, but it works fine just the way it is. People can be easily trained to shoot normal rifles that way. Adding things like this adds weight and complexity, is something else you need to train on, and must decrease reliability. Their site talks all about "instant" reactions. Well, how instant will it be if some part of the system suddenly breaks?
The XM 29 is another extreme example of this. Without the electronic fusing, the grenade launcher is largely valueless. Simpler: what if the optical sight fails on the XM8, or the new AK5s where they are taking off the irons? There are no backup irons, and these are battery-operated sights; they will fail at some time. A co-located dot and iron allows instant regression to a rugged, functional system.
Rolling a normal rifle, allows it to 'twist' without adding hardware, and all rifles do it equally well.