I haven't sat in the new redesigned C-class yet. But, the older one was vastly inferior to the 3 series. Mercedes' one redeeming feature is that it's supposed to feel more luxurious and give a better ride than the BMW. Well, not with the C-class. It feels really cheap and doesn't ride any better. The C32 AMG does feel luxurious and ride's smoothly, but it's got different leather and trim and special seats which account for the ride smoothness that the regular C's don't.
Still, Mercedes redesigned the interior (and exterior) in large part due to the complaints about how utter crap it was. My parents, who generally don't notice the details, were so horrified with it that they actually suggested I not get it, even though they like the brand and defer car choices to me. I haven't sat in the new one tho so I'll withhold judgment until I do. The new SLK supposedly got a much higher quality interior too. Hopefully MB has heeded JD Power and all the customer complaints and is upping the quality. I, for one, have been bitching endlessly about how cheap our E320 feels. The quality on our 85 500SEL was much, much better.