Mark at Kaedrin linked to a great post at Armed and Dangerous about (some of) the motivations in Harry Potter. Mr. Raymond there falls squarely in the Severus is still against Voldemort camp (which I am part of), and I think he does a find job supporting his claims and I have to agree with him. I think Snape is a great character in many, many ways, and one of them is breaking down the bad guy/good guy duality – he’s far more complex than a simple good guy or bad guy. My own prediction for book 7 is that it ends with Snape as headmaster at Hogwarts and Harry as the Defense Against the Dark Arts teacher.