Weird. I had an iTrip for a year and a half and my music sounded fine. The only issue I had was I had to replace the first one, but thats mostly because I had got it off a friend who abused the shit out of everything he owns. Did you make sure your volume on the ipod was turned up enough? I have a different friend who owns an iTrip and he always has that shit real low but then proceeds to rant viciously about how it sucks.
Also, much like how cassette adapters have been around forever, theres fm transmitters you can buy that plug right into your ac and are way cheaper and work better than the itrip.