At this point in time, Man Of Steel is my all time favorite comicbook/superhero movie. I refuse to let anybody ruin it for me.
If anything, the somber ending represented and showcased a Superman we've never seen. When he realized what he did to Zod, it reminded me of when Lois died in Superman The Movie. I think we will see these emotional and moral conflicts resolved in the next movie. I will be disappointed however if that involves being dealt with the entire movie though.
I felt hope throughout the movie and feel that he may have already come to terms with what happened with Zod and who he is and what he is suppose to do and the code he must stand by. That's just the feeling I got.