About the R-Class interior, I think it's fine. It's well made, appears durable and feels and looks premium. It basically satisfied most criteria for a luxury interior. Plastic is used by everyone in the luxury market, everyone.
I think what ruins most MB interiors for people is the general trend towards "conservative styling". The R-Class, GL and ML interiors can be described as "boring" looking, and this probably makes people also think they're "a little cheap looking". I've said it before, the GL and ML interior are good. Perhaps not class leading, but good.
