I have two pair of the HD camera glasses, and I use them a LOT. I think 150 shops on my "old" pair, and another 75 in my "new" ones.
DISADVANTAGES:
1. If you have short hair, then, yes, the wires are visible.
2. You've got to really control your head position; nodding "yes" or "no" creates video that makes the client seasick.
ADVANTAGES:
1. You can wear "normal" clothes (hooray!) - no need for a dowdy shopper shirt.
2. Your angles will be excellent: if you are looking steadily at the target, you can relax, because you are getting great video.
3. You will get superior video in the following scenarios: seated at a desk, ordering fast food, observing a bartender, etc.
4. Some targets are wise to the shopper shirt/button camera setup. Going in to a shop with a plain v-neck, no buttons, throws them off their game.
I love my camera specs. I'm ordering a third set soon, and I'm going to have someone retrofit them into an over the counter set of "normal" frames so they are completely undetectable. And that process will remain my trade secret.