This was really brilliant! I loved the inclusion of the Malfoys and I liked that you had Lucius being pragmatic and a good friend (which I always imagine him as) and Narcissa being slightly off her rocker (she is the one with the insanity in the family after all.) I felt awful for poor Draco. After living with that massive nutcase sadist in his house, having his family and his life threatened for over a year and now his mother trying to get him to kill his mentor and Head of House to make a horcrux... uh, yeah... NOT a good year!!
The Harry /Snape relationship was very realistic I thought. Especially since you had shown that Harry (and then also Snape) had had feelings prior to encountering each other once again. Sex scenes were very hot, nicely different from one another and built up to create the feelings of greater intimacy and commitment. Wonderful story.