I'm currently using one until I can get an [link|http://www.neocaraudio.com/prod-ion.html|iON], Uncle Sam wants some extra money first due to that side job I picked up last year.

It works OK for the most part, but picks up interference every once in a while. Travel too far and you'll have to change frequency which isn't as easy as on the [link|http://www.ipodlounge.com/reviews_more.php?id=6266_0_6_0_M|AirPlay], which I've seen rated better than the iTrip in a few places. The iTrip uses MP3s to send a signal to the iTrip. You have to play, then pause, as the last part of the MP3 has a "cancel" signal in case you accidently play something. The AirPlay has a + and - button for selecting channels.