One of my coworkers has one. Honestly, i think it sucks. The resolution is abysmal, and I found the screen impossible to focus on. It promises to provide super fast access to vital information, but in the use case of looking up a stock quote or reading a text message or using a map, i found it far easier to just look at my phone.
to even make out the screen. i had to adjust it constantly. it would always slip on my face so everytime i needed to look at the screen that meant more fiddling with my hands. for something that's supposed to be hands free, it sure did occupy my hands a lot. Then the crummy resolution results in a hard to see result.
if you think you are going to get useful navigation information while you bike or drive, like google implies, thing again. if you think you are going to suddenly exhibit superhuman cognitive abilities as the whole of the web flashes before your eyes and your friends marvel at your ability to recognize everyone and everything, think again. if you think you will look like you are paying attention while secretly watching something in glass, you won't you look like a catatonic idiot.
However, it's not like it holds no promise. this kind of thing is probably the future. And i want a cool wearable hud in the future so i'd honestly like you to buy this piece of crap now and help fix it.