I think one of the big things that would be great is having a shared space between 2 or more people who can all be in, and interact with, a virtual/augmented environment. Say you and I are working on a prototype of some sort. We can put a model of it in our shared space, and manipulate it together. we can see what it looks like in the real world, touch it, move it, change it, shape it, etc. Tony Stark kinda stuff. Lots of people in maker space, or engineering, design, etc. would go nuts for this I'd imagine. But I think one of the things we lack right now is physical feedback. It's really hard to wave your hands around in the air trying to manipulate something but having no feedback at all. And I don't know what it would even take to make that work. Having gloves with some sort of haptics is a start, but it's not enough.

Otherwise, why do I gaf about my spreadsheets floating in front of me? Watching a movie could be fun, but I can just watch a regular tv and not have a massive headache and feel like my eyes are being ripped out 20 mins into it. If it's just going to be another monitor, then I don't see how you're going to drive mass adoption with that