Not bad-but kinda boring with weird fixations.
This isn't a bad fanfic, per-say; the writing quality and characterization is both very high, and the initial portrayal of snape as a deprived grumpy man and Harry as an abused child are both very good. The trouble is that those characterizations do very little to *change*. In chapter 1, Harry is flinching back from thinking he's going to be hit, and Snape is admonishing him about it, and 30 chapters later, *exactly the same thing* is still happening. There are slight changes, but not enough to be consistent with significant character changes.
Furthermore, the author seems to have something of an obsession with spankings, and bottoms in general. Things got a little weird when Snape, a fully grown man, orders Harry to strip off his pants and undergarments so he can apply some ointment on his buttocks. Perhaps this is just a cultural difference between the author and I, but when I was that age, as a boy I would have been mortified and humiliated to be told to do such a thing, not to mention grossed out. I certainly wouldn't take it as a sign of my guardians affection and love for me.
Other than those two things, though, it really is a decent fanfic. Not top 1%, but top 10% for certain. Consistently good characterization(at least, within the story; the characters are significantly, but not unidentifiably different from canon), writing, and nice insights into the Slytherin House.
If you like WAFF, read it. Otherwise, read the first few chapters and you'll have gotten basically the gist of the entire story.