I use the BB Gateway with my Iphone 4 and works just fine. Quality is good, not spectacular, but it beats FM any day. I stream Pandora and keep the phone in my pocket. With External IPod Control from Cydia you can skip tracks using the volume buttons on the phone. So when I want to skip a song I can feel for the volume button to skip it. And volume is controlled via the stereo system. The phone pairs as soon as I get in the car. Pick a song and it plays through the stereo. When I get a call the car bluetooth takes over and the music fades. After I hang up the song starts again where I left off automatically.
This isnt the best solution but its better than listening to radio. Only real gripe is the car must be running for it to power the BB Gateway. You cant listen to music with the engine off! Why couldnt they make it power on with the accessories? Oh BMW why?