At first when I read the part of the book where he dies I was shocked but at that time I felt he deserved it, after all he was a no good teacher who showed extreme favoritism and hated Harry right? I kept reading to the part where Harry sees his memories and I was slightly dissuaded from believing he was evil but still I thought he didn't do a very good job of protecting Lily Potter's son. I watched each of the movies once then a while passed and suddenly I kept watching the movies like crazy, I would go so far as to say that I was obsessed with watching them. I started watching what Snape did closely and I realized he actually did a very good job of protecting and warning Harry while still being inconspicuous, he supported Harry for the most part and he did seem to try and get past the fact that this was also James Potter's son he was helping, him being hard on Harry in his classes was just teaching Harry as much as possible and he probably got worried Harry wasn't learning enough so he became very strict and at times unfair with him. Of course Harry hated Snape so it would be hard for Snape to keep continuously helping Harry when all Harry was doing was giving him hate and suspicion in return. I realized that Snape had it pretty rough [explained later] and that he did a very good job. When I saw the seen of Snape holding Lily and crying I was truly convinced of his love of her.