The itrip is a very cool unit & I'm very glad I bought one. Having said that, I must point out that IMHO it is not the best solution for in car use. Stations constantly drift, sound quality is marginal at best, and changing stations is too complicated to acomplish while driving.
A better solution is to use a cassette adapter.
itrip is great on the patio for playing through a boom box, or stationary stereo, but in motion it is very frustrating.