Only mildly spoilery, but a major mess regardless.

Rating: 6/10 (5 January 2013)

While I admit to preferring the book versions of most works, I am not a literalist. Movies such as L.A. Confidential used major surgery to transform brilliant but impossibly stream-of-consciousness writing into a singular, excellent, same-but-different movie. It's not impossible and it's not anathema to make major changes.
The Hobbit makes a lot of changes from the text, but very few improvements. A scene is added at the beginning to show some history in an effective, concise way, and I understand the addition of major players at Rivendell to provide a little more exposition even if I found it boringly rendered. (If Galadriel spoke any more slowly, she would be impossible to understand. Every word sounds as if she's emerging from a coma and doesn't know what she's saying.) Really poor changes include the addition of two silly drug references; obnoxiously sugary, cutesy-poo scenes with Radagast the Brown; at least four endless, pointless CGI sequences designed to tie into theme park rides; and an excessive emphasis on childish humor, of the boogers-and-belching variety.
Continued lameness from the movie trilogy includes sword killing that doesn't cause bloodshed, smarmy hugging by characters known for being hard-cased curmudgeons, and the omission of what might be considered negative personality traits in people who used to be complex characters but now must be unconditionally adorable in order not to confuse the simpleminded.
This used to be a tale of adventure, showing a spoiled, untried person having his metal refined through hardship and finding inner strength. There was darkness in this story, and truly harrowing moments, and depth for all the lightness. Now it's just a wacky romp designed for maximum marketing.
They could have made a really good movie and STILL made a lot of money, but they chose to make an overlong, horribly cartoonish, Keystone Kops ordeal.
If you see this movie, and it is eminently skippable, pause during the fight of the stone giants to get a glimpse of the "real movie" direction they could have taken while keeping the fantasy intact. It's not the shifting mountains with the theme-park-ride sliding, not the New Zealand Tourism Board panoramas, but the beautifully rendered, mountain-tall giants themselves, hurling boulders at each other in mindless elemental rage. The single "wow!" scene in the movie.
Imagine the entire work endowed with meaningful situations and purposeful action.
Imagine how much better this movie could have been.