Having tested both the Magic Leap and HoloLens, the biggest problem by a mile is field of view. Everything in this magical holographic world cuts off within a very narrow band of focus. The image is also not very sharp, bright or opaque. Trying to achieve both opaque images and a transparent screen is extremely difficult. As is the processing power to push enough pixels in battery-operated piece of eyeware. It's possible that microLED can bridge that gap, but it's just starting to creep into commercial production. Even with the current limited technology, I have yet to see any remotely plausible mainstream use cases for this kind of device.