I'm still kinda worried about the interface of Google Glass, resp. the actual handling of the device: if you'll be limited to voice inputs and to swiping on the ear piece in the final version I suspect that this device will be not be very usable in an every day situation. esp. when you're using it in public you just might look like somebody who is constantly scratching his head.
I speculate that you would still require a touch screen to do most of your tasks, such as writing instant messages, checking when the trains go or just for browsing the web.
I don't think Glass (or a similar product) will ever be used for intensive tasks, but I think you're underestimating what you can do with gps, wifi, gyroscopes, accelerometers, 2D touch surface and voice.
Writing instant messages? I already find the voice transcription on Jellybean to be faster and easier than a touchpad. Checking when the trains go? Ideally, Glass tells you before you even need it (a la Google Now), but that can also be a voice query. Browsing the web? I don't think that's the intended use case, but touchpad + detecting head position / movement for navigation should make this pretty easy.
I won't code on Glass, but I look forward to never fumbling to get my phone out of my pocket, turning it on, and launching the camera app. That and simple information retrieval queries "Glass, define 'dionysian'"; "Glass, when will Jenny's flight get in?"; "Glass, what's the surface area of the Sun?" will by themselves make glass worthwhile for me.
I speculate that you would still require a touch screen to do most of your tasks, such as writing instant messages, checking when the trains go or just for browsing the web.