I took my 9 year old son to see the movie this past weekend.
All in all, Id say I enjoyed it. But reading the book before you see the movie spoils you!
If the movies were made to the detail of the books, they probably would be at least 12 hours long. So its understandable that some elements need to be cut out. But just 10 or 15 minutes could have made a big difference!
SPOILER ALERT - Among the details from the book that were left out of the movie:
* Harry explains what happened to Dudley. Aunt Petunia knows what a Dementor is,
and receives a howler from Dumbledore.
* Ron and Hermione are selected for house Prefects. So is Malfoy.
* Rons brother Percey now works as an assistant for the Minister of Magic, Cornelius
Fudge. He distances himself from the Weasleys because they believe Harry. He writes
a long letter to Ron, congratulating him for becoming a prefect, and warns him to
distance himself from his family and Harry.
* Harry, Fred, and George are barred from playing Quiddich at Hogwarts by Umbridge.
* Ron becomes the Griffindor Keeper, Ginny becomes the Seeker. They beat Slytherin
for the Cup.
* A centaur, Firenze (from the first movie) takes over teaching Divination when
Trelawny is sacked by Umbridge. He is attacked and is ostracized from his herd
because of it, and Hagrid squares off with the rest of the herd of centaurs.
* Hagrid is sacked by Umbridge. He is hit by multiple stunning spells from Umbridge
and a squad of Aurors. Professor McGonagall is caught in the cross fire and is
injured. Hagrid is half giant, is unaffected by the spells, and proceeds to beat the tar
out of the aurors.