What is the best known result concerning the existence of companion forms for classical modular forms?  Gross' tameness criterion paper is always mentioned with a "unchecked compatibility" caveat?  Are the results in this paper bona-fide theorems?  The Coleman-Voloch paper on the topic (which does not rely on these unchecked compatibilities) seems not to allow k=2 (but Gross' paper is fine with k=2). Does Khare-Winterberger's proof of Serre's conjecture trump all of this?  If so, is Serre's conjecture known unconditionally now or are there still unresolved cases?