There's always one.  Every good thing has a dissenter, and that's me.  The ATH-M50 cannot handle songs with lots of different lower frequencies going on at once because of the artificial bass extension.  For example, Nine Inch Nails' "Heresy" is a very challenging song to play on headphones; it sounds like crap on my car stereo because the subwoofer is confused on which notes to play, so too low of frequencies overpower what should be playing louder.  The M50s do the same on the FLAC version of it.  The impacts of the kick-drum are far quieter...