1. We don't get to watch the Quidditch World Cup
2. It pretty much gives away Tom Riddle Jr. from the get-go.
3. The music. John Williams's absence is far more painfully obvious than "Prisoner of Azkaban". The birth of Voldemort scene could have used much better music.
Other than that, very well done. I give kudos to Mike Newell. His directing sort of has a Terry Gilliam-ish feel to it.