I have a jawbone. It's nice in that it also works on both of my cell-phones and has noise-canceling technology. My complaints:
1) It does 'hang off the ear'
2) It can be hard to hear other people on it
3) My dad tells me that when I call him while outside on an even mildly windy day, it sounds like I'm in a wind tunnel. Guess the 'noise-canceling' isn't as great as they advertise it to be.
4) Requires a proprietary charger cable (included, but sucks you can't just charge it with any old cable)
Pros:
1) It's good looking. You don't look like a complete tool when wearing it in public
2) All the buttons are recessed, which is nice.
3) Charges over USB, so easy to charge on the PS3.
4) Comfortable on the ear, even after long wear.
5) Has a reasonable resell value if you decide to get something else (see ebay)