I finally went and saw this yesterday. The 3D looks very good, though your eyes know something weird is going on and both eyes and brain end up doing a bit of extra work. The 3D nevertheless stood in considerable contrast to that in the previews, which was heavy on the gimmicks.
The story was very engaging and Pandora is beautiful. There were no surprises in the story, perhaps, but I thought Cameron treated his audience intelligently by not trying to pretend we didn't know where it was going. It would be a great movie even without the 3D. The only slight hiccup I thought was the other male researcher - Noel, I think? I got the sense that a storyline was edited out there, with him initially resenting the main character when he began achieving so much. Easy to shrug off though.