I use the Dilo fm transmitter/recharger car mount w/ lcd. Cost is $100, but it's waay convenient. Sooo much better than the itrip.
I wouldn't want to hard wire my ipod...the point of it for me is portablility. I'm not in my car all the time to justify it and ipods cost too much to have multiple.
SOunds fine for my purposes...car is too loud to listen to anything other than loud, so any minor hiss or background is not heard.
look up the dilo unit in the ipodlounge.com
the problem is that it's white and bulky. Still looking for a better mounting location.