I've been happy with the sound quality both directions, but not with the sunroof open. I also have the mike mounted on the roof close to the sunroof, and the wind naturally makes quite a racket for the listener. Not bad on city streets, but forget it on the highway. I tend to close the sunroof when I make or receive a call.
I don't use the voice dialling (always feel like I'm doing a lame imitation of a Star Trek episode), so I can't speak to how well/badly that works in my car.