And to those of you who saw the film in the same theater type I did, did the movie appear to be projected a tad dimly? It did to me, and I can't blame it on the theater. This one is usually very high quality and is only a few years old.
I've seen it in a variety of settings, and dimness was a problem on one of the RealD screens I saw in on in Colorado. I'm not sure what projector they used, but it was dimer then it should have been. The best showing I saw was at the Alamo Drafthouse, using Sony 4k projectors and RealD. The brightness was almost too much, as minor flaws in the screen were visible for brief moments, but thankfully not distractingly so. I'd say it could very well be an issue with the theater you went to.
The biggest issue with the 3D was that my wife and I had had to strain so hard to see the image properly, and afterward, we had the worst headaches, ones that seemed focused entirely behind our eyeballs. Ugh. No thanks.
I've never gotten a headache or eyestrain from watching it, with IMAX 3D or RealD. I could definitely see a headache problem using active glasses though. If you were having to squint a lot to see the image clearly, something may have been wrong with the setup, or how you were trying to look at the movie. In the proper setting and tech, the 3D experience shouldn't tax your vision at all. Almost makes me wonder if they had a slight focus problem. It would be harder for the projectionist to tell with the way they see it without the glasses.
And lastly, the whole movie was great right up until the credits. Then Cameron felt the need to splash AVATAR up on the screen in giant bold letters, which seemed super cheesy to me. But then it got worse, with the song that played over the end credits. That song is horrible. Ugh.
Up till the end, the movie had no title presented, nor any credits. The movie just starts. At some point it needs to be displayed.