I've been thru several BT headsets with my Treo 650 and my latest is the Jabra JX10. I was also looking at the Plantronics 640 but based on reviews and user comments decided to go with the JX10.

BUT!

As a person who has a Treo 650 AND a work supplied "Blueberry w/Blacktooth"
the Plantronics 640 is a great device for users who need 1 BT headset for 2 phones. The Plantronics 640 has Multipoint which allows you to connect the headset to two different BT phones. It works great as I tried it yesterday. I paired the 640 to the Treo 650 and the Blackberry 7100T, called both phones, and was able to answer both.

I am now wondering if the Plantronics is the way to go. The JX10 does have better incoming/outgoing sound but being able to use the 640 on two phones is a bonus.

Just wanted to throw this out there as I just happened on a post were someone was questioning this.

Is Plantronics the only BT headset company that can do this? I see the 510 and 640 only seem to be able to.