I think the framing sequence was entirely too long. They should have just gone straight into the story instead of blatantly doing a "LOOK THIS IS A PREQUEL, NOW HERE IS FRODO IN AN ENTIRELY POINTLESS CAMEO".
The Hobbit novel came out before the LotR novels, so they should have just treated it like its own story, rather than shoehorning it in as a prequel an throwing in excess winks and nods to the LotR movies.
Other things... This movie is definitely a lot faster pace than the LotR movies, but I didn't get a sense of any of the Dwarf characters aside from Thorin. Next closest to being developed is Balin probably (the old one).
The Stone Giants thing was kind of weird and had no explanation, so it was just "Hey the mountains are alive now, and they waited until we were standing on them to start fighting". It probably had some sort of explanation in the book, but it has been ages since I have read it.
Next point: Did I miss something after the Goblin Town escape? They escaped into the daylight, but then suddenly it was nighttime again and they were being chased by Azog and the Wargs (good band name). Just some bad editing, or what?
Final point: The Eagles really need some sort of backstory in these movies. Right now they are just this giant deus ex machina that shows up and does a fraction of what they could. It just leaves me going "Why didn't they fly them all the way to the mountain?" in both trilogies.
I think I vaguely remember in the book there was some plot point about the King of the Eagles owing Gandalf a debt, and that he could call on them a certain number of times.... but that they hated carrying people/people riding them for whatever reason. (But still did it begrudgingly).