I'm not a fan of things with extra hoses/wires/etc...but on that same note tons of guys have comm lines/lanyards/hydration lines/packs/belts/etc...all over them anyways.
I've got two in the workshop right now...they're very impressive re. build quality and design. The setup/electronics are very simple and it works.
There's noise and all that...no real action to speak of. Sort of like a PTW (switch trigger, instant shot, etc...). Very consistent FPS delivery. And it's fun on a SAW like setup. In fact...that's where I'd see it having the most appeal. To lay in with a lot of rounds without having to worry about mechboxes/batteries...that's cool.
I'd run one on a SAW in a heartbeat...I wouldn't use it for an M4.