The Hobbit was not shot for 3D! I can only say this so many times. The action sequences you speak of had far too many quick cuts and were too close in on the action. Even in 2D I couldn't make head nor tale of what I was looking at half the time. in 3D, this translates into abstract garbled mush.
I agree with Andrew that the first part of the film was the most enjoyable, mostly because the cuts were less frequent, the motion was tightly controlled; this is how 3D ought to be handled.
**SPOILER ALERT FOR ALL BELOW**
There are severe problems with this film even on the script level. So they want to make The Hobbit 9 hours long? I don't actually have a problem with that. I'd love to know what Gandalf is up to when he mysteriously disappears on a rainy night . . . except for he doesn't. Tolkien's The Hobbit is a tightly written masterpiece, primed and ready for a faithful film adaptation.
There is more than enough room in 9 hours for both the original intact narrative and plenty of epic additives ala Gandalf's away time. Instead, the best aspects of every original chapter were altered, leaving the charm of Tolkien's style dead and lifeless.
There's something charming about Bilbo inviting the wizard to tea and ending up with 13 dwarves in his home.
There's something charming about Bilbo signing the agreement, then waking up and thinking it was a dream, only
to be rushed out the door by Gandalf without even a pocket handkerchief.
There's something charming about a cold, rainy night river crossing, when the rain has got into their clothes and
the wizard is suddenly nowhere to be found. There's charm in the elves teasing the dwarves with song as they
enter Rivendell.
And there's something scary about running through completely dark, cramped goblin caves with nothing but the
light of your swords, which are only lit because there are goblins on your heels. Where did all the light in the
underground scenes come from anyway?
Surely Gollum's eyes don't give off all that light in his cave.
They have nine hours in which to tell this story, the least they could do is include all the riddles.