I have a M6 with low miles (48800) so my comments need to be viewed in that context. I have no experience with the M635. So far the car has been very reliable. There are some maintence items that need taken care of but they are not unique to the US version -- suspension alignment, a leak in the self-leveling system and a intermitten coolant leak that I have yet to diagnose. As these cars are relatively rare as you know, repair costs are high in general. A major engine repair for either version would cost as much as a good used American car probably. Is it worth it? YES!!