After using the Logitech Mobile Freedom Pro (the one that clips on your ear via a spring loaded earpeice) and having issues with volume of the PDA, I decided to try the Jarbra M500

Big Mistake -- it is constantly scratchy, and the signal jumps from strong to one bar (red) when the headset is two feet away with direct LOS. The Logitech may have set the volume on the 6600 seriously low, but atleast the damn thing worked.