I run the Pioneer AVIC-N3, which is a DVD based navigation system. It features a retracting screen, which I personally like for security purposes when I park in public places. When the car is off, it simply looks like a regular aftermarket CD player. Functions with a touch screen, directions are exemplary, and there are 11,000,000+ P.O.I. (points of interest i.e. restaurants, schools, gas stations, etc). It seems much more user-friendly than the Porsche stock system.
Also, it allows me to use the same screen to switch between my iPod, XM Radio, Regular Radio, CD, MP3 CD or watch DVDs on long trips with one touch of the "source" button. All the while maintaining a clean look without extra wires or an ugly satellite radio unit.
Best of luck with your decision ...
