I can't even begin to tell you the hell I've been through with other BT headsets and the Treo 650. They all had pairing issues - either they won't pair with the phone or they don't stay paired.  And the volume was not loud enough.  I returned at least 5 headsets until I came across this one.  The sound quality is maybe an 8 out of 10 but the volume is unbelievable, and this coming from a guy that doesn't have the best hearing.  I can actually hear the person on the line - all the time.  Even in noisy environments.  No complaints from people on the receiving end except when I'm in the home and the mircowave oven is running (this will scramble almost all BT frequencies).  Buttons are placed well and they are very responsive.