I have an MFD3 installed in my Octy, but as of yet do not have it coded to the car.

What is the actuall point of coding it to the car, other than the compass indicator coming up in the Maxidot what other advantages does coding have?

it will stop the car generating fault codes regarding the nav controller, and give you some control of the headunit using the trip computer controls on the wiper stalk. In addition you get nav data on the maxidot as well.