STS had an awful interior and everyone panned it for having such.The STS always got hammered when it came to the interior. The CTS has some plastic, but I think its pretty nicely done and its high quality.
Lincoln addressed the interior. Heres the good thing, the only part of the last MkS's interior that was a problem was the center stack. Its fixed, and now no one can complain about it. (Save Cars.com, because they hate anything from Ford)