I've watched my POA DVD three times already since it first arrived on my doorstep last Thursday! It's definitely the best movie so far, which is good because it's definitely my favourite book so far. You can tell Cuaron is having fun with the material instead of just jumping from plot point to plot point.

However, there are a few changes I'd make. First, I'd shorten the following scenes:

1. Aunt Marge inflating and floating away (I'd make her inflate faster)
2. Harry flying around on Buckbeat
3. Harry and Hermione getting tossed around by the Whomping Willow

They're all fun CGI scenes and they do have their place, but I'd shorten them and use the space saved to communicate the following plot points:

1. Show the Wolfsbane Potion
2. Explicitly say that MWPP are Remus, Peter, Sirius and James
3. Tell the story of WHY WPP chose to become Animagi!
4. Explain that Harry's Patronus is, in fact, his father!

It's one thing to assume the viewer is familiar with the backstory of the first two books/movies, it's quite another to assume they're familiar with the backstory of the current story. It's more important to make everyone's motivation clear than to have cool CGI effects.

I'd have also enjoyed a longer Boggart scene, and the Gryffindor vs. Ravenclaw Quidditch match (which is one of my favourite scenes in the book).

And for any Canadian Potter fans reading this, am I the only one who is reminded of Wormtail every time I see the name of Minister of Foreign Affairs Pierre Pettigrew?