I love this hero. He is such a difficult and mystic personality. I think that not a single person in the book won't be able to understand him, 'cause his inner nature is so complicated. He is clever, he is talanted, he can restrain and conceal his emotions and thoughts so geniously.
Snape had a very hard life and his terrible character comes just from the sufferings he had since his childhood. And my opinion is that by the end of the story he will show himself from the heroic point of view. Perhaps he'd die... But he'll do it for the sake of Harry.