I really enjoyed the scene where the kids were learning this and practicing with the Bogart. You mentioned before the attention Lupin gave to Neville here, which sets up later work in the DA between Harry and Neville. Neville is a great character and undergoes quite a transformation from start to finish (primarily between Order of the Phoenix and Deathly Hallows). Also, the fact that Snape catches Neville picturing him in his Grandma's clothes was priceless.

I like Lupin's reaction to Harry stepping up, and the cooresponding explanation of why he cut him off (after Harry gets all sulky). Plus we get the little glowing orb hint about Lupin's "furry little problem."