Yep so much for dreaming. From some brief playing and knowing several developers playing with these...

The glass display is quite difficult to read in full-daylight. It often works well in a car if you have a roof over your head. In bright direct sunlight it is very washed out.

Battery life can be very limited, very dependent on application/usage. You'd need a power connection or external battery pack for long flights.

The display is far from immersive. It's a small display in the top of your viewing area. See the simulation in the Google promo video here http://www.youtube.com/watch?v=v1uyQZNg2vE So kind of big enough to display basic info, not too big to be ultra distracting.

What is interesting is for many different uses how Google and others have condensed information into such as small display and made it very useful.

What could you display for a glider? Vario, STF, L/D required, distance/direction to a turnpoint, (in PDA/PNA parlance you'd probably only display one two or three "nav boxes" of data) look up frequencies for an airport/ATC etc. simple stuff like that.

As pointed others have pointed out without head tracking things like direction to... type information is not that interesting. With head tracking, better daylight visibility (and maybe a larger display) you might potentially be able to do much more interesting things like direction/distance to a collision threat/buddy/turnpoint/airport etc.

Swiping the side of the glass' trackpad sometimes is annoying, requires a few tries. I think its a much worse UI device in a cramped cockpit than buttons/switches/trackball on a joystick.

Voice commands could be interesting but I'd like to see them integrated into the flight computer. Maybe as a thin UI layer to a flight computer/PDA/PNA glass could provide that, but it may be a lot of hassle to go though just to get that. You might as well run that on more modern PNA/PDAs.

So all in all, I think there really is not something here to excited about, at least for quite a while. There are many more practical/interesting real-world applications for glass.

Darryl