Phone for Toyota Prius Bluetooth

I just bought a Toyota Prius with integrated "handsfree profile"
Bluetooth, but my current carrier - Sprint - has no
Bluetooth-capable phones. I have a terrific plan with Sprint,
but will probably have to move to TMobile.

TMobile offers the Sony Ericsson T610. I've seen various
comments on that phone, but nothing regarding its Bluetooth
capability. Hence, questions for the gurus here...

Is there a better phone choice than the T610, and if so, why?

I understand that the SE Bluetooth phone originally intended for
Sprint is no longer in the picture - something about SE deciding
not to make CDMA phones. What is the reality?

Will phones suitable for the car also work for other Bluetooth
headsets by Jabra, etc.?

When Bluetooth (on the phone) is always ON, is battery life
affected much?

Thanks!