Ben's the one running the protetype, I talked to him about it the other day. They're just running it on a 35 but they've stuck some big ol' heavy boggers on there to test it.
He said that so far they've broken quite a few shafts, and I think one lock ring. They redesigned the ring and haven't broken one since. There was some talk before of ripping the air ram off the cover and it looks like they've taken thought to that, there's a beefy 1/4" guard that covers it, theres looked like it'd taken a beating and won.
I haven't ran it so I won't give any insight (don't want to start another one of those threads), but I will say that I like the air ram on the outside, it's the same sort of idea Tibus has on their lockers, no compressed air inside the dif means less leaks and wasted seals.