Is your opinion based on a more modern Mercedes? I can't speak for the new stuff, but the owners manual for my 190d is pretty informative. Maintenance items are pretty well laid out, including serpentine belt size and routing, bulb and fluid specifications, how to change bulbs and even how to emergency pop start. Granted this is for a 1985 model where there aren't nearly as many "see your dealer" and "danger NoNo" warnings.Maybe a thread on the worst manuals might be more informative.
I have two to add to that list:
Mercedes Benz
Audi