i think i would've added a little bit more dumbledore involvement in the 5th book. i mean it felt to me like jk wrote it to accompany the death of richard harris so it would be easier for the movie people, compromising the story a bit. plus i mean harry could've found out more clues about his past than squeezing every explanation and detail into one chapter. thats the only think i was anal about...like the whole explanation was in one chapter. thas bout it though the books ARE brilliant!
Those are all really good suggestions!
The one thing I would change is the Quidditch match where Harry lost to Cedric because of external factors he couldn't control - I would change it so that it was made known and there was a re-match at least cos he would have got the snitch otherwise and deserves his spotless record. The reason for my choice is that I really didn't like it when Cedric's dad was bragging about it to Harry's face, come on he's just a kid and the game has nothing to do with the fact that he's 'Harry Potter', it's purely down to their performance. I hate it when people rub it in or unrelated things into it, it's just rude.