 Like many German cars, this has its quirks. The navigation is tough to get used to, but that's not what's most curious about this car: at elevation about 10,000 feet, the nav shuts off! It displays a warning and becomes inoperable. Mercedes says it affects so few people that they won't fix it. So if you drive in the mountains a lot (we live in Colorado) and want to use this car in high elevations, keep this in mind.  As importantly, keep in mind that Mercedes refuses to spend the time reprogramming the nav systems. Maybe they outsourced that part to Japan...