Poorly maintained MBs can be a real pain in the butt -- defered maintenance is expensive, particularly the little stuff. The main reason I do my own work, couldn't afford one otherwise.
Don't forget, though, the longevity -- my 220D is thirty years old, and if it had been maintained properly, would still run well -- it "only" has about 160,000 miles on it! Other than a few worn things (tie rod end, flex disk), the 300TE drives pretty much like new.
Germans take a different approach to automobiles and auto upkeep -- they feel it appropriate to replace things on a regular basis Americans want to last "the lifetime of the car" -- or 5 years, 100,000 miles. Flex disk every 60,000, valves every 160,000, etc. Difference in philosophy. For sure the MB will, properly taken care of, last 30 years. American and Japanese cars don't.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!