In the words of that old dude from the end of Indiana Jones and the Last Crusade: I chose "poorly". It's a cute little transmitter, but - at least in my van - my radio couldn't pick up a clear signal unless I manually held the iTrip up against the face of my radio (and yes, before you ask: I tried nearly every frequency up and down the dial before giving the iTrip the i-boot). I decided that maybe I needed to spend a little more money and exchanged the iTrip for Belkin's TuneBase. Since it has an adjustable arm and base, I figured I could position it exactly where it needed to be for a more reliable signal.
The TuneBase proved to be a better choice mainly for that radio proximity factor, but using an FM transmitter in general proved to have too many quirks for me. For one, neither of these units pumped out a strong enough signal, so I always had to crank the volume on my stereo to reach a proper jamming audio experience. But if I switch to the radio, or simply skip a track on the iPod without manually adjusting the volume, blaring static pours through the speakers until the FM transmission kicks back in with a new song from the iPod. Ultimately: it just felt like too quirky of a device and too much of a compromise to pay $50 (iTrip) or $80 (TuneBase), so I settled for a good ol' fashioned $15 (non-iPod branded) cassette tape adapter from Best Buy for now.
But what about you, music-loving TUAW readers? Are you happy with your iPod FM transmitters? Which one are you using, and did you need to get creative with any workarounds? I wish I could find a solution for both the Astro and the Matrix (especially since the Matrix's gas mileage is killer), but so far my efforts have failed. Share your thoughts and teach me (and hopefully others) your ways!