That story seems a little overblown to me, but I think it does have some good points.
I think the build quality on my new C is quite good, I don't notice any misaligned seams, bad stitching, etc. like they point out in the article. And, the car seems as tight as a drum.
But, it certainly doesn't have the "over-engineered" feel of my Porsche 911, or even the feel of my '86 BMW. Both of those cars, despite their advanced age, have a "solid" feeling that the new MBs do seem to lack.
There are also some materials and details in the C that do seem a little "cheap", both in the interior and under the hood. The cupholder comes to mind. And the headliner, too.
That being said, I paid around $32K for the car, brand new. Not cheap, but not earthshattering expensive, either. Overall, it meets my expectations so far for a car of its price. For example, I did not feel that the E46 3 series(current body style) is superior in build quality or materials than the current C. Nor was the Audi A4, in my opinion, or any other of the MB competitors. (although they certainly have closed the gap).
Now, I DO wonder about the S, and the new E. One of my big surprises was at how similar in quality, materials and looks the new mighthy S and my lowly C are. While the C seems to use materials commensurate with its price, the S does not strike me as a $90,000 car.
We plan to keep our C for 15+ years, so it will be interesting. I take very good care of all my cars (which are now, with the exception of the C all over 15 years old and function basically "as new"), and will be very disappointed if the C does not hold up well over that amount of time. Only time will tell.