I've got a T610 that works pretty well. It has a few small issues that I would like to see corrected. For starters, there is no ring when receiving an incoming call for instance. The radio shuts off and the phone screen comes up, but no ring, at least not one I've heard.
Also, when you transfer the phone book from the phone over to the Prius, only one number per name shows up. Many of my listings have two or three numbers, so I have to go back to the phone and manually dial it. To that end, you cannot manually dial the phone or look up a number on the Prius phone book while the car is moving. I understand this is being prevented for safety reasons, but it's not very practical. Am I supposed to pull over to the side of the freeway if I want to make a call? At least give me voice activated dialing.
Finally, there doesn't seem to be away to make a call from the handset while the phone is connected to the car via Bluetooth. If I want to do this, I have to disconnect the Bluetooth and then dial the phone. But then it seems, you cannot reconnect the Bluetooth unless you turn off the car and restart it. Again, not very practical if you're cruising down the freeway.