In the book the battle is in the middle like all the other LOTR books. This is not particularly logical in narative sense, but thats par for course with LOTR, the horrible pacing is part of the charm of the novels.
I agree that a lot important stuff was missing from HP3. Most importantly they didn't even explain who the four makers of the maruaders map were at the end, I think that is pretty important.
My wife summed it up well, she's an even bigger Potter fan then I am. She said as its own movie, POA is good. But when you watch the first film, about 1minute into it, when you first see the scar on Harry's forehead and the title appears, the music swells, you get this feeling in your gut, the Harry potter feeling and its there throughout the whole movie. You pop chamber of secrets in the dvd player afterwards (as we did the other night) and there's that feeling again, right away you feel like your still in the first movie, and as soon as Harry jumps in the car with Ron to escape the Dursely's its back in full force and even stronger then in the first film.
But you never have that feeling in this one, or very rarely. Its fine that its dark, I like dark, but ti seems to have lost a lot of the heart along the way. The Lupin/Harry scenes were great, but the rest of the movie just left me so empty, and when the last shot froze the way it did and I heard Harry's voice over I half expected some cheeze ball rap song to come up. I scanned the credits to see who did the music for film3 think John Williams had either not been brought back or had chosen not to return, his wonderful theme from the first two films (his best work since Indiana Jones and the classic trilogy starwars) plays once during the Warner Brothers logo at the beginning and then is absent for the entire film. This was such an odd choice to make, that music is such a huge part of the Harry Potter movie success formula IMHO. I always listen to the soundtracks when I read the books now.
Hopefully I'll like the movie more on DVD, it would be sad to think the best book produced the poorest movie. But then that happened with LOTR IMHO so it is possible.