Really good when it comes to how to use it ... When I first plugged it sounded lousy. The base was distorted beyond recognition, and all s-sound jarred. I was pretty fixed on that it would return to the store! But then I turned the volume down just a bit on the source, and then cleared everything and it sounded super. You can hear some background noise while songs with a little silence in, but there is nothing to interfere.
You just have to find the right balance. If the volume of the source is low, the quality is much better, but the background noise is heard more since you have to turn on more on the radio.
Have tried a cheaper transmitter that sounded pretty much the same, but that was before I realized that the volume on the source was too high, so I really have nothing to compare with the quality.