I bought a C-class nearly two years ago. It has been chronically unreliable and very poor quality. It has been back to the dealer over twenty times for warranty repairs. The most annoying faults are constant creaking from windscreen, dashboard and B-pillar. Mercedes simply cannot fix these faults - they now insist that these are "normal" noises....
I also had to complain for nearly a year before they fixed a wobbly seat, and eight months before they accepted that the navigation was faulty. The stereo has been replaced twice, various other electrical things at least once each.
I have been through my diary and in total it has been in the dealer for sixteen weeks in 92 weeks of ownership. Is this a record?
I am simply fed up with having to take the car back all the time, and so have decided to just sell it and accept that buying a Mercedes was a huge mistake.
Just one data point I know.