I recently had a '16 plate Merc C220D for 3 weeks as a courtesy car, following someone driving into the back of my IS on the M56. I can comfortably say that if that is an indicator of Mercedes build quality, I will never EVER go near one to own. It only had 7000 miles on it and squeaked, creaked and rattled and had a very crashy ride - this was on 17"s with plenty of sidewall - which looked tiny on the car as it's ridiculously large for a 'small' saloon. Not only that but the diesel engine was dreadfully noisy with no refinement whatsoever. And don't even get me started on the naff shiny plastics on the dashboard, or the enormous intrusive info-tainment screen that is just seemingly stuck on the top of the dash, that has no touch control features.
Coming back to a replacement IS, it's so much better screwed together, and a far more pleasant place to be.