This story was really clever - it definitely changed direction from where I thought it was going at the start, and I really enjoyed the missing moment here, and getting a glimpse into the way that Dumbledore's Army start operating their resistance.
I am not a massive fan of Snape, but I actually really enjoyed him in this story, and found myself wondering at the way that he had to behave during this year to try and maintain his double agent role. I don't think he troubled himself too much about the feelings of the students - particularly the ones who caused him most trouble - but he was ultimately working for the same cause and he must have had some twinges of conscience.
The fact that he invited Ginny up to his office to discuss the Gryffindor Quidditch team actually makes me wonder whether he intended for her to see the Sword of Gryffindor - I wouldn't put it past Dumbledore or Snape to realise that Ginny and the others would probably try and steal it so they could take it to Harry, and that would then give him the chance to smuggle the real sword out of the castle and actually give it to Harry.
Still, even if that was his intention, he managed to maintain a pretty inscrutable veneer, which fits well with his character. I'm kind of curious if they ever were allowed to reform the Gryffindor Quidditch team, but I loved the fact that Ginny went straight to Neville with what she'd seen - it shows how much she trusts him, and that they were already working together at this point. A really enjoyable missing moment.