That Michael Shannon will be anything less than awesome as Zod. I've seen what he's capable of from clips of Boardwalk Empire and Take Shelter and want to see him go truly psychotic! I'd love to see him go as crazy on Supes as he's been on Boardwalk Empire! Can you imagine how awesome that would be?!
I'm not worried about Cavill's accent. Most of the movies he's been in have been directed by non-Americans, and MOS is his first big American movie, with a director who's so American that he uses "awesome" in every other sentence.
So I think Snyder would've caught any of Cavill's accent slip-ups.