I purchased Jawbone II from AT&T last night and I can give my first impressions.
After 2 hours of Talk Time...the headset was comfortable to wear for an extended period of time. It fit my ear from the factory without trying out all the earloops.
The first person I conversed with could detect that I was using a BT headset Suggesting, "your service isn't very good where you are." He knows I have AT&T.
The size and fit is wonderful! It rests against the face whereas the Apple BT Headset always came out of my ear and when seated stuck out from my cheek. I feel Aliph found the sweetspot as far as size and design is concerned. The headset emits a white and red LED seemingly from nowhere (much like the iSight LED on a Macbook). Volume is adjusted on a scale by touching the back of the headset; the highest setting is WAY TOO LOUD and showed some distortion.