I really don't know what to believe as far as reliabilty and quality anymore. I have heard great things about Lexus. I have heard great things about Mercedes. I think they're both really nice cars. The Japanese auto manufacturers simply take a different approach at luxury rather than the German.
Well for the W140 that my mom has, S350 diesel, it's been alright with problems. The engine went out at 50k miles but that's only for the diesel 350. Both windows in the back stopped working. This was at 45k miles. Antenna stopped going up and down but that's because of the salt in the winter.
Other than that the car has been pretty good. But again it has very low miles. It's a 1994 model and it barely has 60k miles.
1985 500SEL 124k miles
2001 Honda Civic EX