I've been using one for about the past month. Here are the high points (as compared to the Plantronics Voyager I used to use):

pro:
-mini USB charger, so no longer have to carry a dedicated charger
-voice prompts are very nice
- pairing is easy
- relatively comfortable to wear for long periods of time
- voice quality on both sides is generally good
- talk time is very good (I use it a couple of hours a day and it never seems to run out of "juice")

con:
-occasionally drops the connection in the middle of a call (used with an IPhone). This is not a huge deal, just an annoyance
- ear piece volume does not go high enough to easily hear quiet-voiced people in loud environments
- I can't seem to figure out how to train voice prompts to use people's names when the caller ID recognizes the name of the incoming call. This may just be a failing on MY part or an issue with my phone however
- cannot say "answer" until the voice prompt finishes receipting the incoming call number. With international calls, that can take a while....


Bottom line: I give it a moderate thumbs up. I don't love it, but I think it's probably one of the best ones I've seen so far.