First, this was the first time I have seen a feature film in IMAX, and it sort of reminded me of when quadraphonic sound came out and lasted briefly: the records that came out had lots of thumping, roaring, crashing, and surprise sounds coming out 180 degrees apart. All for show, of course. Same thing here. I enjoyed seeing Harry and his pals disapparate with a snap - again, and again -- but did not appreciate the excessive sound. SInce I mentioned quad sound, it may be obvious that I am not in my twenties. Maybe if you are twenty-something, you enjoy having your ears de-sensitized. I don't. Enough said.
This particular episode was a disappointment, since it felt like a road trip. Now there on some beach, now in the woods, now briefly on Diagon Alley. Not much in the way of direct conflict or character development. I am looking forward to the final movie, since it will have all the great revelations of the final book that this one could not include for reasons of length. I understand why they decided to make this the transitional episode, to get us to that final, thrilling point, but I don't sympathize. Maybe I'm just weary of Harry and his dilemma. It could be worse: I could be watching another Batman episode. (Nooooooo!)
Any HP fan will probably go see this regardless of what people say about it, but if you are saving your pennies, I would save them for the next episode, and reread the book. Your ears will thank you for it.