Below is a thread on the headset problem.

http://discussion.treocentral.com/sh...ght=tcjohnsson

A lot of people, including me, can't stand the unacceptable levels of distortion generated by the headset-out. The 600 clearly has a problem with the amplifier circuit for the headset. I really hope this problem is addressed on the 650. Anyone compare the sound quality, specifically of the headset, between the two phones?