I finished up the first chapter with my Hardcore character, and holy crap is the Butcher scary. It's kind of absurd considering how little trouble I had with him every other time (a few on Normal, and again on Nightmare). I thought that I was done for once or twice, and my heart was thumping once I realized how easily he could kill you. The only thing I can liken it to in games is the hardest boss fights in Dark Souls: that intense desire to live against all odds is something absent in almost all games (it certainly is missing in Diablo III on any other setting). It won't last: I'm sure that the frustration from dying will be immense, but the feeling I got today fighting the Butcher has certainly led some credence to the validity of the mode's existence.