I have a Cimgular Branded, reflashed to Unbranded Fully Unlocked 650. My version can not at present pair with the 770. There is a list on the Forum that shows the status of most of the more popular phones out there. The TREO 650 basically says "some do, some don't"
I just finished typing a response to someone with a SMT5600 smartphone. Go read that and that will fairly much clue you into the situation. Short version, I too love my new 770, but the Bluetooth, NOKIA not only dropped the ball, they forgot even catch it.