Just installed an AVIC-N1 in a 2002 BMW M3 SMG Convertible. The Wiring was simple for everything but the VSS wire, which is located in the Speedometer cluster. It took a little bit of probing to find it, but once found it was perfect.
The VSS wire is the Black wire with the White Stripe on the Tachometer side wiring harness of the Speedometer cluster. It was not located in the radio harness as I had been reading around the net.
The reverse lamp wire can be found on the right side of the trunk it is a blue wire witha yellow stripe.
The rest is standard simple radio wiring.
Of course you can hook the green wire up tot he parking brake as the manual states, or you can ground it so that you can watch video when driving.
Overall I like this unit, wiring is not too hard at all.
The biggest concern is mountign the hideaway brain unit, which I found putting under the drivers seat to be the perfect place, I found it was nice and easy to make it level.
Matched up with a CD changer or DVD Changer, this unit would be a great unit to use for someone who wants navigation and video capabilities. the only drawback, is the nav cd has to be in the radio to use the navigation, it's navigation memory saves 1 route, but if you want to listen to an audio cd and do navigation at the same time, you are better off getting a cd changer or DVD changer.