what do you think the average fan would not notice in the movie?

The movie has pointless scenes and they took out others crucial parts to the narrative

at the very beginning where fenrir greyback has just emerged froma store, he's captured olivander for use in the Deathly Hallows :)

The fact that Tonks and Lupin seamed to be togehter allready (she called him sweet heart), but her hair was brown and not pink. (and missing Dobby...)

I don't think they would get the full importance of the "Half-Blood Prince" and they wouldn't notice that Harry knew to use the Bezor from his book, and not his head.