Judging it on movie merits alone, I thought is was good. However, as a big Potter book fan, there were many things that irked me.
1. So much was explained in the book but left out of the movie: the reason Harry got his scar, why he must stay with the Dursleys every summer, the explanation of the full prophecy ("...marked as his equal..."), how Harry was able to survive Voldemort's attack, why Voldemort attacked Harry in the first place.
2. The movie altered a few plot points or left others out completely: Ron's Quidditch victory and S.P.E.W (left out completely), Kretcher's role, how Umbridge found out about the DA, Trelawny's role in the prophecy, the centaurs.
3. The movie never mentions Umbridge's role in sending the Dementors to Little Whinging.
4. The scene in which Harry sees his father pick on Snape was never developed. This really affected Harry's feelings about his father and Snape.
5. In the book, Dumbledore defended Harry by putting a spin on everything Fudge said. He made Fudge look like an idiot. In the movie he begs Fudge to believe that Voldemort is back and give a brief statement about Harry using magic in self-defense. I don't think this speech was convincing at all in the movie.
7. I didn't realize it until later, but Percy Weasley did make an appearance, but unless you now the story from the book and have seen the second movie, you would now he was there. The movie never mentions his estranged relationship with his parents.
6. Lastly, why did members of the Order refer to Voldemort as the Dark Lord. Harry makes a point of saying only Death Eaters refer to Voldemort as the Dark Lord. (This is one of the arguments in favor of Snape still being loyal to Voldemort; he still refer to Voldemort as the Dark Lord). Nobody else refers to him by this title.
I did like the casting; Dolores Umbridge, Bellatrix LaStrange, and Luna Lovegood were perfect. And I loved the sets and effects.
Sorry this is so long, but my husband hasn't read any of the book so he has no idea what I'm talking about. I have no one to vent to here right now
Thanks for listening; I feel better now