I just got a $130 Sony Xplod head unit with their $50 iPod connector kit. Very similar to the Alpine kit. I used to use a cassette adapter, which sucked. I tried a couple different FM transmitters, but couldn't find a bleed-free frequency I could stick with while driving around the metro Baltimore area.
This Sony also has a line-in jack on the front. The sound quality on that is better than the cassette adapter, but pales in comparison to the dock connector solution.
Installed, with the wiring harness and all that extra crap they spring on you, it ran almost $250. Well worth it, IMHO.
Of course, now I realize how badly I want new speakers in my truck.
