Don't recall ever "regretting" knowing the books behind the movie so well ( read the series front to back twice ) But before i get flamemails. I liked the movie, but certainly wouldn't take my young kids to this or any of the potter films ( too young )
Just found myself thinking that they were working too hard setting up for the finale, not building a full experience for a single movie. Will admit the emergance of the 2 faces of Draco ...from a truly "Evil" young man opposed to nasty boy ...then easily switching to the very human scared young man at his special "moment" which he thankfully fails at! was remarkable !
Enjoyed seeing Snape, now finally becoming the true hero he will eventually become! Enuff said...