Google Glass won't be the only eyeware computer. There will be many others, including:
Contact lens computing (not real yet)
Meta-View (Like contact lenses, but in glasses form instead)
Oculus Rift (complete virtual reality headset marketed to gamers)
None of these devices directly compete with one another or Glass because very few of the applications for any of these devices would work on the others. Each device provides a totally different experience.
Although these devices differ in many ways, there is one key attribute that will define how the device is used: transparency. Why is transparency so crucial to adoption? Because humans need to maintain eye to eye contact for basic communication and interaction. It's incredibly de-humanizing to talk to something that looks and acts like a human, but that has robotic/android eyes. The eyes inject life into the human face. People will not stand to interact with those wearing a device that covers the eyes unless it's understood that the device is paramount to the task at hand. Transparency and the ability to maintain clear, direct eye to eye contact will dictate how eyeware computing devices are used.
Through the lens of transparency, let's walk through the transparency of each of the eye computing products that have already been discussed.
The contact lens solution is by far the most transparent. As the video demonstrates, contact lens computing could impact literally every aspect our lives. Contact lens computing presents the logical extreme of frictionless, transparent, and ultimately "real" computing. Unfortunately, this is probably still a ways out.
Next is Google Glass. Glass was designed from its inception to be, as Google phrased it, "there when you need it, and out of sight when you don't." Google is envisioning a future in which everyone can quickly access the information they want when they want. In order to accommodate that, Glass must be acceptable in public. Google has gone to great lengths to make Glass as invisible as possible.
Next is Meta-View. The creators of Meta-View share the same vision as the products of the contact lens video: "real" computing. Meta-View is simply bound by current technology limits. Unfortunately, that means no one will communicate with anyone wearing the device. Even still, it's amazing to see someone working on this idea.
Oculus Rift is at the far end of the transparency spectrum. It's beyond opaque. It places the user in an engrossing virtual reality in place of actual reality. Of course, this will never reach high usage mainstream adoption, but it will be incredible for the hardcore gaming market, training, and other enterprise applications. Perhaps the masses may use an Oculus Rift-like device as an occasional novelty. There could be opportunities for a movie theatre type model where people go to venues to use an Oculus Rift like technology for a short period of time.
Eyeware computing will manifest in many unique form factors. Each will have unique characteristics designed for unique applications and experiences. For at least 5 of the next 10 years, eyeware computing will experience an era of hyper-innovation, just as multitouch glass smartphones have over the past 5-6 years. This is going to be a hot industry for a long time to come.