I also don't think this will become a successful product. Technology isn't there, yet. People aren't there, yet. Without the first it will be even harder to achieve the latter.
For now, there are very, very limited uses for this technology. I haven't seen anything Glass can do, my Smartphone can't do multiple times better and faster. Even simple things such as calling someone or looking something up. Speech instructions are problematic and still don't work that well. Apart from the fact that you might not always want to tell everyone around you what you're currently doing or whom you want to call. Again, technology isn't there, yet. Input and interaction is just too limited.
Classic computing devices, even those so called post-PC devices have an interesting characteristic. Whenever you use them, you clearly indicate those around you, that you do so. You don't look suspicious. You look "normal" and your posture tells everyone around you "hey, i'm not available for a chat at the moment, cause i'm clearly checking my email". This is even true for other forms of wearable computing, such as watches, etc.
Glass is just different, it's creepy. It is not immediately apparent whether you are engaged into something or not. You look stupid. When you stare at your screen for longer than a second you look like a creep or a zombie. Most of all however, people feel threatened by this face mounted device more than they feel threatened by Smartphones, Cameras or even Smart Watches. Simply because taking a picture with any of those other devices requires a clearly distinctive gesture. Doing this with Glass doesn't. I really don't blame people for rejecting it. I wouldn't want to talk to anyone with Glass, either.
Purely technologically, I don't think it is there, yet either. Not even close. I also don't think having a device mounted permanently in your field of view on one eye only is good or healthy, and there have been opinions about that as well. I believe it will take at least another decade for the technology to mature, similar to how tablet PCs have taken a long time to get to what they are today. When the day comes, where we can keep on wearing regular glasses, however with a built in HUD, which comes up whenever we want to and when interaction comes to a level of really advanced eye tracking or brainwaves or whatever, then the world might be ready for it.
As it stands, this is simply a creepy toy with questionable benefits.