I have a 2007 Mazda CX-7 with a stock radio so no MP3 jack or usb slot. For $140 (basic installation is included - it rings up as $90 for the unit and $50 for the install), I can now listen to and charge my iPod in my car. I use MOG and Slacker (cached stations) and both apps continue to control the music just like when you are using ear buds but the volume is adjusted thru the car stereo knob and/or steering wheel controls.
I have the newest 4g iPod touch and, although it's VERY snug, the adapter does fit it just fine. For whatever reason, it's not nearly as snug when plugged into my sons' iPod classic.
I highly recommend this product for anyone that is considering it.
By bnord from Minneapolis, MN