It is very lovely that this fic is so long, the better to appreciate their slowly growing friendship. Their relationship was so well written it carried me along very pleasantly all the way through, and the little bits of plot add some nice variety along the way.
I love how it started! Mrs. Weasley is so wonderfully portrayed, just as I imagine her. The surprise of Snape's survival, and that it's Molly who sets them up, was so satisfying to read! That might be my favorite part of the story. The silver sparks as a symptom of Harry's problem was a great choice, so very visual, and with the heat and the melting and the unpredictability, it had lots of delicious tension - especially when it finds a match in Snape. Besides, the way it puts Harry's magic out of whack was such a cuddly way to bring out Snape's habit of taking care of Harry. :D