That depends on what you consider "major" complaints. Care to enlighten us which ones you're referring to?
The lighthearted atmosphere, the "deus ex machina" saves literally all the time, the too fast pacing to name a few.
I don't see these as the major complaints here though. From what I've read in this thread, a much greater and more valid complaint is about the way the movie tries to combine
the lighthearted atmosphere with the dead serious epic tone of the LOTR. Complaining about a lighthearted tone in an adaptation of The Hobbit and calling it a "fault" would be quite silly, IMO, and most likely to come from those who hated the book in the first place. And the complaints about too fast pacing I must have overlooked, I only noticed those about too long and cheesy action scenes.
Regarding the "deus ex machina" argument, while it is true that The Hobbit has its share of "deus ex machina" solutions, my complaint with the movie is, that it makes them all the more evident by even adding more of their kind. The book has Gandalf turning up out of nowhere and saving the day twice or so, plus the eagles. The movie has that too, but it also has the party making a wondrous escape from each and every dramatical action scene LOTR-style, both heroes and enemies constantly falling over the edge just to make a surprising return, a small hobbit without combat training pushing over a huge muscled orc warrior four times as big as him etc. etc. Lots of cheap action tricks that threaten the suspension of disbelief.
The movie could have made an effort to smooth away the story-telling 'flaws' of the book instead of amplyfying them. How about trying to explain why Gandalf happens to be in the right place at the right time, for example, seeing that the movie already made him one of the main characters with his very own scenes? The moth was only a half-hearted attempt IMO, since neither the moth nor Gandalf's relation to Gwaihir were introduced beforehand, so it doesn't do anything to change the fact that it's a deus ex machina solution.