I have had the Griffin model, and before that another one called the iRock (which only gives you four station choices! it sucked) to use when driving, and the sound quality can be excellent, but only if you are not in a heavily populated area where all sorts of other FM broadcast signals interfere with yours. Especially on long drives, you will need to occasionally switch around and find an unused station.

So I agree with Goober, if you are using it when driving get a cassette tape adapter instead. Way less hassle and the music will stay good and consistent.