Okay, so when I first got my Jawbone, I thought it was great. But after I had it on for more than 15 minutes, it started hurting my ear...needless to say, it ended up spending way more time in my glove compartment than it did on my ear. Since then, I've gotten to use the Plantronics 925 a bit. It's much more comfortable than the Jawbone just because it's a straight ear bud rather than an ear...hook. And amazingly enough, once you get the hang of putting it in your ear, it's pretty stable. I think the sound quality is quite good. It doesn't have the same tingy sound of the Jawbone.
Plantronics Discovery 925 Bluetooth Headset Reviews
I really like my Plantronics 925 bluetooth. It's a lot more comfortable than my Jawbone because it doesn't have that annoying over-ear piece. I also find that the sound quality (on my end) is better and it's quite effective at cutting out ambient noise (for the other person who you're calling). I'd recommend it.