I just used Google Glass at a technology fair in my school. Here are my thoughts.
Appearance: I thought they looked awkward. If you've seen pictures of Glass, the right side appears very clunky. Guess what? It is. I have a quirk with symmetry, and it irritated me how asymmetrical Glass looked. I'd be much happier if the computing component was slimmed down.
The frame is just a single piece of bent metal with two 90° turns. It looks like you're were wearing a headband that fell way too low. Not exactly stylish or attractive. There's no frame around the lenses, and I think it looks awkward. Let's hope Google's partnership with Ray-Ban improves this.
5/10
Comfort: Here's the thing that impressed me the most--I didn't really notice the comfort. This is excellent. When you wear a product, you naturally expect it to be comfortable. Only when things become uncomfortable will you notice the level of comfort.
Despite how clunky Glass looks, it fairs well when you're actually wearing them. The only thing I noticed was that you need to position Glass well over your right ear (the side with the computing component). If it's too far forward or back, you'll notice by how it feels on your ear. Not a big issue when you have them positioned, but I felt it needed mentioning.
Overall, Glass is lightweight and comfortable.
9/10
Function: I've never had a display so close to my eye before. It's not uncomfortable, it just feels weird for a bit. I became used to the display after a minute or two, but anyone who has the chance to put them on for just a few seconds may jump to conclusions. Don't do that.
A small, rectangular display appears in the center-right of your vision. It's clear, though I wouldn't call it crisp. It displays the Glass UI which allows you to view menus, see what you're recording, etc. I didn't have trouble reading anything from the display. It looks like you're viewing an iPhone screen about two feet from your face.
Once you figure out the touch commands by touching Glass's right temple, the UI is fun to navigate. Swiping up and down on the side of your glasses is fun, as weird as that sounds. It's a subtle way of controlling an interface and I love it. I think it's a very effective way of controlling Glass, and it feels as natural as adjusting your regular glasses.
The video quality is by no means beautiful. The camera is better, but still not very good. Think of phone video quality circa 2008, and that's what you have with Glass.
The speakers/templephones are good for all intents and purposes when you have them positioned correctly on your face. I'm not sure how much walking around/commuting will affect the quality of Glass's sound; vibration is audible when Glass is incorrectly positioned behind your ear. Don't use them for listening to music and you'll be alright.
Finally, the voice recognition is stellar. I expected no less of Google, who has let users search by voice for years. I told Glass to "record a video." "Ugh," I mumbled. "I didn't say 'okay Glass,' then 'record a video.'" To my surprise, Glass started recording right then and there. Stellar.
7/10
Conclusion: I think Glass is a pretty fantastic gadget if you feel a need for it. I'm sure most people will get along fine without it, it just brings more convenience to having a smartphone. I'll round the overall rating of the product to a solid C. It needs work. Would I ever wear it? No, not in its current form. If Google sells the computing component for consumers to attach to their own glasses, I would definitely consider.
If you have any questions, feel free to ask. I'll do my best to answer.