Soon enough the category will be a replacement for your home theater and/or your mobile entertainment device (i.e. tablet).
As simple as it might look, the most compelling mass-market use case I saw from Apple is... watching a movie on an airplane.
That experience is pretty crappy on current headsets because the resolution is low and the optical aberrations are very noticeable. The dual micro-OLED approach solves those problems. As production ramps up on micro-OLEDs the category will become 10x more affordable, and within 10 years I'd be surprised if 50% of people on commercial flights are not wearing this kind of headset.
To borrow a Steve Jobs phrase, I think of these devices can eventually become "a bicycle for the senses"[1] and open up all kinds of exciting use cases. But to get to mass-adoption you have to nail the basic stuff like watching a movie or TV show. We just haven't had a good device that can do that yet.