I wouldn't have thought I would like this... I do read het but switching the genders of main characters really usually turns me off. I think why I ended up liking it so much was a) how you kept it so delightfully kinky and b) you kept Snape SNAPE, despite him having taken on a new persona. It played much more as him in "spy" mode yet retaining his true personality and that was just lovely.
Really enjoyed this and was truly surprised. You made me love something I don't even like! Great job on a really difficult job of getting characterization right with this.