I thought this third movie was by far the best of the three. The first does a good job of intoducing the characters and environment, but I can barely even stomach the second one. I liked Prisoner of Azkban a lot. You are correct that Emma Watson is the best of "the three." Radcliffe is also getting better while Grint is watchable again after his incessant whining in the second movie. In my opinion, though, David Thewlis steals the acting honors in this movie. Oldman was also good, but not in it enough to outshine Thewlis.
The most merciful thing in the world, I think, is the inability of the human mind to correlate all its contents. ... The piecing together of dissociated knowledge will open up such terrifying vistas of reality, and of our frightful position therein, that we shall either go mad from the revelation or flee from the light into the peace and safety of a new dark age.
~ Howard Phillips Lovecraft