This is a very good movie, I quite enjoyed it. I agree that under 13's should not go - there's a lot of violence and some sexually themed content that would be a bit much for younger children. There are no real surprises plot-wise in the move; you can figure out almost the whole story from the trailer and every major plot point is telegraphed by a mile. For all that, it is visually stunning and I did enjoy seeing it.
It is long, but not unduly so and I didn't feel like it was overindulgent or in need of some prudent editing. The review notes a parallel between current events and what's happening in the Middle East, but I think it's more intended to be an allegory to the historical treatment of American Indians and indigenous peoples around the world by explorers who "discover" their lands and force them off. I couldn't help being a bit saddened by what I saw and reminded of how shameful our own history is in this regard, but there could be value in it for discussing with older children to give them insight into history.
All in all a good story well told and worth the trip. 3D didn't contribute anything special to my experience, however, and I wouldn't recommend paying extra for it.