I see frontline workers use those thing every time I interact with them, far more efficiently than anything real demonstrated in a Hololense video so far. If you're working with your hands, it's very likely you can't afford to have you FOV obstructed by much. For example, I'd freak out if I saw a surgeon wearing one. I'd much rather they be looking at a magnified view, fed to a high-speed 2D display than a laggy 3D approximation of reality.