Basically, the thing gives you some screens fixed in world space. You have to be mostly stationary for the effect to work. So it won't replace walking around staring at your cell phone. A lot of thought has gone into the interface for this sort of thing. That's the real achievement here, and that matters.
Workplace of the near future - a room full of people, crammed together as on an airplane or in a theater, each wearing a headset. No more desks!
It's still too heavy, though. If it's tethered to a belt-mounted unit, why isn't the electronics down there, instead of in a brick on the back of your head? The headgear part needs to drop to no worse than swim goggles.