i love my factory one, also subs as a DVD player so i can watch movies on my nav screen. THe newer factory ones are also used ot view your ipod, cell phone and for idrive you can check all your car info.
i just looked at this sort of system to put in my coupe...screen slides in and out so it's hidden while parked. $2,150.00 incl. tax and install.
aftermarket of course.
still .. too much for me right now. maybe in a few months.