I really wish that Cumberbatch was anyone but Khan, really. By him being Khan, Into Darkness basically became a more action packed version of Wrath of Khan, which is idiotic. They could've taken far more creative liberties if they'd used a character like Gary Mitchell (my top pick) or Kodos (my second pick). I actually think that both concepts for those characters are brilliant, and it could've been such a good movie. Actually, the more I think about it, the more I think Benedict Cumberbatch should've been Kodos.
Granted, he did play Khan very well, but that's because he's a bloody fantastic actor.