First off, I do not have toys to communicate with Glass. I realize that Glass is too early. There are not enough data dumping devices available at decent prices. Withings, vehicle data, health data, all the things people try to keep private. That kind of data is what would be useful with Glassware.
The lack of a SDK and depending on RESTful services. I want to toy with sensors too. Delayed gratification does not work. Where are my long nights of programming?
Battery life and destroying my cell's data plan are also issues. I'll miss watching people's faces light up when they try it on.