I sell a few of these, and other brands at work.
The iTrip is probably the best (cheap) model I've used, but of course cause it transmits over the FM bandwidth it's gonna be very vunerable to interference, and the quality is also extremely limited. Well, when I say extremely limited, it's gonna have nothin on a CD, but if your satisfied with how your local FM radio station sounds I guess it'd be good enough.
Personally I'd look at wiring a Line In into your headunit man, way better sound.
