I've got the Motorola T505. I like it since it has an FM transmitter so I can also play my phone through the car speakers. The sound quality is what you'd expect for an FM transmitter but it works well enough for me. The people on the other end of the call can definitely tell you're on handsfree as the call quality is ok depending on how close the unit (and mic) is to you on the car visor.
http://www.amazon.com/Motorola-T505-...4678488&sr=8-1