using the ear piece, I am usually able to switch between calls without a problem or at least what thats what I remember.
I did use wired ear piece with my Blackberry alot for convinience of not having to recharge Bluetooth all the time, so that maybe confusing me.

Sad to know that there is a limitation.

BTW, how long does it take for you guys and gals to have the phone paired when you get into the car and are on the phone, did you have the phonecall in limbo for 20 or so seconds?