The issues with the movies that I have, and really, they've all been fine, despite no clear cut great flick from the group is that Goblet of Fire and Order of the Phoenix were real hatchet jobs in that the story was fine, but they weren't able to elaborate on it much at all.
The first two movies held to the books for the most part, outside of some liberties taken as a director, but after that, the films starting to pack too much into a small time frame.
Azkaban was solid. But after that, Goblet of Fire and Order of the Phoenix...needed a lot more time. Half-Blood Prince was fine as they did a fine job editing and getting the meat of the story, although suffered similarly as the two before it.
This last film was smart in that is divided it up as two films, with a lot of slow, mood capturing scenes in 2h15m of film before they really let the last film run with the important shit.