What is really missing at the moment is a method of controlling the display. Waving your hands in front of the camera is not an attractive option to me, but there are other possibilities once the tech gets there that seem much more seamless:
* Controls on the glasses themselves - not much better than waving hands.
* Some other sort of control device you can hold, like an apple remote with more buttons - could be very flexible, but again ties up your hands.
* A wearable device like a watch or wrist-band - could be quite unintrusive and should be possible fairly quickly.
* Embedded sensors on the body or the fingertips - obviously a way out but these could give great control simply by tapping on the leg or arm. Even typing is conceivable.
* Subvocalisation, sensors near the throat or head that can pick up subvocalised or whispered commands - speaking is pretty slow for control commands, but could be great for dictating messages.
* Brain control, sensors that can pick up thought patterns - this seems futuristic, but some advanced tech can already move a cursor and even dictate some words using this. Shouldn't be hard to choose from a HUD menu if designed well.
Ok, maybe I got carried away, but I'm pretty excited by what this sort of tech will be like in 10 years, especially if we can use contacts instead of glasses.