Many techs I know consider the W202 series 1996 and on to be the most reliable MB ever built, with the M111 equipped car especially so. The engine is very well made, has no head gasket issues, and after 1995 the wiring harness issues that plagued all 1993-1993 MB's were also sorted out.
Also, the post 1996 cars have the variable pressure AC system, which is also proving to be very reliable and robust.
Be careful of overfilling the engine oil, as the main crank seals can easily be wrecked by doing so. Make sure your PPI includes a close inspection under the car.
Also, the W202's that live where roads are bad can go through lower front ball joints.
There is mixed feelings on the Eaton M62 supercharger mounted on the M111 Kompressor cars. Eaton supes have long been built as sealed non-rebuilable units with a typical service life of 100-125K miles. While this is suitable to GM products, most MB's are still valuable and excellent cars at that mileage. However, the verdict is still out on this, and I understand M62 pricing has come down lots since it is being used in many applications.