I have a Jawbone Prime and a Motorola H15. They are both great. People can't tell I am on a headset, even driving sometimes. In my opinion, the incoming audio is more natural to me on the H15. The Jawbone can be tinny sometimes, but still fine.
One thing I like about the H15, and why I tend to use it when I am going to be on and off the phone, is the boom flips out to turn on and it connects VERY quickly. The Jawbone can be a pain if it is off and you need to turn it on and get it on your ear. The caller could be gone by then.
Just my $0.02!
Z10 and PlayBook <- 9650<- 9630 <- 8330 <- 8130 <- 8830 <- 8703e <- 7130e <- 7250