I bought one of these at the Apple Store, but brought it back a few days later.
Finding a clear channel here (Munich, Germany) was a pita, basically there are none so I ended up unscrewing the car antenna to get it to work.
Sound quality was nice then, but in the end I invested in a new car receiver instead (after some googling for reviews, I chose the
Kenwood KDC-BT6544U, which cost only a little less than twice the amount of the FM transmitter).
Now I can access my playlists from the radio itself, and the phone charges, all with one single wire (the original USB to dock connector one that ships with the phone). Plus, it's got Bluetooth Hands-Free built-in.
Other products with similar features are made by Sony and by Alpine, most of these come for roughly 180 to 250 bucks.