Best child actor:
Rupert Grint (aka Ron Weasley). Not quite how I imagined Ron, but all the better for it - he gets the edge over Harry due to his superb style.
Best child actress:
Emma Watson (aka Hermione Granger). Perfectly annoying, extremely clever and a know-it-all, she wins hands down.
Best special effect:
Fluffy. It was a tough choice, but he moves very well and looks good, while the Quidditch match isn't quite up to scratch.
Best addition from the book:
The extremely funny, improved "Dudley and the snake scene". He falls into the water and after being paralysed with fear, ends up trapped in there. Stupid boy.
Most disappointing thing to lose from the book:
Peeves the Poltergeist. A comic, mad and all-round mischievous character, he would have looked good on the big screen rather than the cutting room floor. Oh, well.