There are no volume or brightness controls, and these aren't automatically adjusted either. As a result, you can't hear Glass in a noisy environment unless you cup your hand over your ear. And in dim light, when your pupils dilate, Glass' super-bright screen is uncomfortable to use. In my case, it made my eye feel sore after I did a hangout that lasted about 20 minutes. (Such a hangout in brighter ambient light or with a dimmer Glass display would have been fine.)
Also: The sound technology is bone conduction. But other people can still hear it if they're nearby in a somewhat quiet place.
Glass is best when you have a fast-connection Android phone (to which you pair via Bluetooth), plus the Android app, plus an external WiFi connection. When you eliminate any of these elements, Glass becomes less useful. For example, with Wi-Fi but no Android phone (even if you connect to an iPhone), you can't get turn-by-turn directions.
Everybody's freaked out about Glass users taking privacy-stealing pictures. But the truth is that taking pictures is obvious. You either say "OK, Glass: Take a picture," which is loud enough to hear for anyone within 15 feet away, or you press a shutter button which looks just like taking a picture with a regular camera. As soon as you take the picture, the screen lights up conspicuously. When you take a picture, people near you know it.
Video can be more easily done in secret. The reason is that you can get the video started privately then keep it running as you approach people. People can see the screen lit up over your eye, however, and if they're really close they can actually see themselves in the video. But if people don't see you start the video, they probably won't assume you're recording one.
If your smartphone had no apps except for a camera, phone, maps, a few social networking apps, email and notifications, it would be about as functional as Google Glass is right now.
The real revolution lies ahead when developers create apps we can't now really predict. (My advice is: Never say you'll never get Glass because you'll likely change your mind when the killer apps start coming.)
Despite all its beta problems and the social weirdness that happens with wearing something so new on your face, Google Glass is truly life-changing for the better.
I've never heard other Glass user write or say this, but I think the biggest benefit of Glass is how it "feels"—or how it affects your psychology.
Taking pictures and videos feel a bit like memorization; Google Now information feels a little like knowledge. Hangouts and phone calls through Glass feel sort of like telepathy.
Glass makes you feel like you have extraordinary mental gifts and even super-powers, rather than being merely the user of devices that let you do pretty much the same things. And that feeling is strangely compelling and possibly addictive.
Wearing Glass all the time, then suddenly going out into the world without it (or without battery power), makes you feel naked, limited and powerless by comparison.
So here's the truth about Google Glass as I see it: The technology is both more ordinary and more revolutionary than you may think. You're probably going to get one, or something like it, within the next three years when it works better, looks better and has thousands of apps.
And—it's an overused cliche—but Google Glass really is going to change everything.