I've had 3 BT headsets for the 650.  The Jabra unit that was being given away with the 650 when it first came out was a piece of junk and very irritating for the ear.  The Treo branded headset was a great improvement, except that people always complained my volume was too low and I found some calls were too faintly heard, pairing of the headset to the phone was 50-50 when I received a call, headset control of the 650 were tough to access. Got this unit because the battery was going on my Treo and I wanted to see if something better was out there. So after 5 days experience, I can say that the H700 is superior with respect to call volume on both ends, pairs with the phone nearly 100% of the time, and reliably can control the phone.  Main problem is that the H700 roaming range is poor, sometimes giving poor reception on the other side of my body. However, this is outweighed by it's virtues.  Some have complained that the boom control to answer the phone does not work, but I found on some Treo BT forum that when the unit is set up to choose the car kit profile.  Recognition does take several seconds, but this is an endemic problem of BT units.