Save yourself 900.00 and the remounting of your climate controls (on Nav equipped cars the climate controls are in place of the top compartment above the ciggy lighter) and buy yourself quite possibly the world's best REAL navigation system, the Magellan Roadmate 700. This is based on tried and true technology, the same found in Hertz Neverlost equipped cars, it uses a totally upgradeable hard drive system, and is ultra precise with SUPERB voice prompting and audio/visual notification. MSRP is roughly 1400.00, but these go on ebay all the time for as little as 950. I used the Hertz system when on business in California and would highly recommend it.
Also alot harder for thugo types to steal when you can pull it out of your car. Other than the TV option, I dont see a real reason to go with the BMW based unit.