What's there to be said about Shannon? He's perfect in the role. He's got some incredibly wonderful subtle moments during his confrontation/battle with Jor-El.
But what I love most about the character Zod, and it was really handled in a fairly subtle way...yes, the guy's not totally evil, which we're told and shown pretty clearly. But more to the point, he was genetically BRED to be loyal to his planet and his people. He doesn't really necessarily have the ability to choose his destiny like Superman does. He may not even be able to. And it leads him to do terrible things, including to his former ally. It kind of makes Jor-El and Lara's decision that much more powerful. That's a really cool concept.