It's incredible. Very clear sound for both phone and music usage. Music audio is very good, maybe not CD-quality good, which would only be possible with a direct-connect, but certain clear FM-quality good.
I much prefer it to an earpiece, which I only wore in the car anyway, only now I don't have to sit with something in my ear for and hour whether I'm on a call or not. Plus its really cool looking. Highly recommended.