I'm taking delivery of '08 3.0si a week from Tuesday at the Performance Center. When ordering I asked my dealer about the USB and iPod connection and what he would recommend. Her is his e-mail reply.

the difference on the I pod is that the USB cable allows you to adjust your play list’s and everything from the steering wheel or I drive as well as charges your I Pod! With just the Auxiliary you have to do everything by actually using the I pod and it does not charge your Ipod. Hope this helps you I will plug in your order on Monday and Email it to you J