See, I was one of the ones who ALWAYS thought that Snape was good - not for one second did I ever believe he was working for Voldemort. He's definitely one of the most, if not the most, complex characters in ther whole series...if you hadn't read the books already, you'd probably think he WAS evil. And Alan just does such a fantastic job as Snape - I think he's a big part of the reason Snape's as popular as he is.