Piffle. It's like any of the other 3D things I've seen: blurry, distracting, and in no way enhancing; I bet the film works much better without it. It is, I grant, better than other 3D things I've seen, in that there's less of the obvious wave-in-your-face sequences, but it only really works when things are moving slowly, so the camera can keep up, and even then, it's just there: it doesn't help.
As for the film itself? Well, the easiest way to describe it is that it's a poor script made into a poor film, very, very well. It looks utterly gorgeous, the CGI is amazing (when the 3D isn't getting in the way), and everyone portrays their characters very well. Ironically, each and every one of those characters has two dimensions less than the production, but never mind - what little there is, is portrayed well.
But oh god, the script. The crap, weak script. Jim, it's taken you years to make this - couldn't you have spent just a few more days giving it the depth you've put into the technology?
In case you're not familiar, the film is set on another planet, where the Evil Corporation wants to mine the shit out of everything to get their hands on the valuable Unobtainium, and feeling vaguely offended when the blue-skinned (note: not redskins) indigenous population objects. The Corp has high-tech gunships, heavy artillery, mercenaries and a healthy respect for the dollar; the natives have bows, arrows and more Nature-based spirituality than David Attenborough marinated in a bath of 100%-proof Essence of Druid. Sam Worthington, wheelchair-bound marine, is getting to know the local tribe by remotely operating his avatar, a manufactured native body, so that he can find out what it'll take to convince them it's worth their while to move.
Everything happens as you'd expect, from the above.
 Literally. I thought they were kidding, at first.
Here be spoilery text.
There are a few dumb technical things. Worthington's avatar gets lost and cut off early on. What, no tracking systems on these hugely expensive biological investments? Not even basic radio comms? The Evil Mercenary Commander sends in a whopping great bomb that has to be delivered effectively by chucking it out the loading bay of a Hercules due to magical "flux" screwing up computer navigation. What, no ballistics in the future? And, god help me, they've got mecha.
We won't even go into the silliness of a twelve-year round-trip to another planet to collect something. God knows what Unobtanium does, but that's a lot of investment.
But more importantly, there appears to be absolutely no conflict within Worthington's character. No peaceful resistance. No qualms about using deadly force on his own people. Nor do we see any of the previous resistance that the natives have supposedly been putting up - three arrows in tank tires are all we have to support that. Nor is there any indication that the natives are having any problems in their lives that technology can't help (they're tool-users, so they've already lost some of that battle).
I confidently expect this to win special-effects awards (and possibly make up). Anything else would be criminal, though (or indicative of a very poor year in Hollywood).