I bought mine 1 year ago and have put 20k on the car with no worries. It had 152k at time of purchase. This is my fifth older mbz and is my favorite one of them all. Fun to drive, great reliability and the interior layout is practical. I have seen the 3.0 liter inline six go 400k plus with just a top end rebuild. Things to be aware of: head gasket and engine harness failure. A small price to pay in overall upkeep, for a car that is safe, has classic lines and can handle high mileage with proper care.
We bought this car with 147K on it. We had it checked out and were told it was in great shape. It came to us with a failed transfer case leaking a qt of hydraulic oil every 100 miles. The repair was nearly $2,000 and the part very difficult to come by. Now the front and rear engine seals are leaking and the engine has to come out. That will be another $2,000+. The water pump and alternator failed within days of each other. There have been numerous hard start problems. This is all within 4 months. The car is fun to drive but I don't trust it to go more than a month without needing some hideously expensive repair.
This is my 4th Mercedes-Benz product and it has been troble free. Never has it stayed over night in a shop. Maintance is more expensive than domestics but the quality of the job is far superior because of the dealerships' high levels of quality control. If the car needs new breaks the dealer does it right the first time, every time.
This car was purchased with 23K miles in 97. I initially was shocked with some of the repairs i.e., motor mounts relaced again after 5K. Electrical flaw in the hatch $600. The radiator neck broke twice along with the fan and polybelt. Then at 76K the 4matic went out which was the biggest hit of $2300. Other than those items the car is a workhorse. I plan to keep it for another four years then sell it and buy a 2000CL500. I should be able to afford one by then.