Having actually been asked about it - by a commenter, and everything! - I would have to say that the movie did what it set out to do. It was not a standard Japanese 200 foot monster film; it is a film about people stuck in the middle of a Japanese 200 foot monster film, and as such, it works. The camera work is a personal-taste issue: it didn't distract too badly for me, but I can see where shaky-cam might annoy. The monster may have been a little too visible, towards the end... but that may just be my latent "this would have been cool if it had been Cthulhu up there" attitude talking. JJ Abrams wasn't going for cosmic terror; he wanted horror-excitement, and he generally got it. Well worth the matinée price
That's about it, except that there's already talk about doing a sequel, and frankly, I hope that they don't. This was essentially a gimmick film - I say that without meaning it as criticism - and I'd rather that the gimmick not be revisited.
PS: The theme music was excellent, and placed at the end of the movie, where it would not distract. Watch until the end credits.