I have to say, I'm pretty impressed, and my excitement for the movie has been upped by several levels.
For one thing, it's pretty cool just to be looking forward to a Middle-Earth movie on the big screen again - it has been well-noted that this winter has been a full ten years since The Fellowship of the Ring was released, and by the time There And Back Again comes out it'll have been ten since Return of the King.
And it looks the Hobbit film was worth waiting for. It does seem that the tone has been modified a bit to make it more consistent with Lord of the Rings, but given that Tolkien himself did almost the same thing, I don't see that as too much of a problem (as long as it's not taken too far). Frankly, on account of this I'm surprised at the presence of a couple things in the trailer - mostly the quick glimpses we get of the Dwarves throwing Bilbo's plates around gives me hope that we'll actually hear some of Crack the Plates song the Dwarves sang to tease Bilbo.
On the other hand, from the trailer it does seem as though several of the other lighthearted elements are getting a change for the grim, as it were - that scene with the mounted elves circling some of the dwarves doesn't look like it'll have much tra-la-la-lallying, and the brief glimpse we see of the trolls seems to indicate that they will be somewhat more primitive than in the book.
I suppose some changes like this were inevitable, if only to make The Hobbit map a bit more closely to The Lord of the Rings. Peter Jackson and company can't really be faulted for this, though, since Tolkien did pretty much the same thing when he adjusted the ending of the Riddle Game (and apparently he was planning a third revision to be published in 1960, though the project was abandoned when it started becoming too divergent).
But hopefully the film won't be going quite that far. As I mentioned, from the looks of things at least a few of the Dwarves' goofier antics will be present, mostly in the presence of Bifur, Bofur, and Bombur. Especially Bombur.
And, speaking of things whose appearance in the movie causes relief, soon after the trailer appeared came the revelation that Thorin's cousin, the great Dwarven warrior Dain Ironfoot, will definitely appear in the movie, portrayed by Billy Connolly. While perhaps not the first person that comes to mind as "actors who should play Dwarves", I for one think that bit of casting has a lot of potential:
"Khazâd ai-mênu!"Humor aside, though, everything I'm seeing so far has me really excited for the movie. So far, it looks as though it will be about on par with The Lord of The Rings in most respects, though covering some of the action away from Bilbo and the Dwarves (note the appearance of Galadriel in the trailer, as well as Gandalf wandering in a spooky place that may be Dol Guldur) is, perhaps, taking a bit bigger risk with The Hobbit's tighter narrative.
Of course, come December I'll be in the theater either way. Whether I'm pleased or disappointed won't be known until then, but after seeing this trailer, I'm thinking the former far more likely.