Perhaps ironically, Avatar was the movie that turned me off to 3D. I actually enjoyed and appreciated it more on my TV without the glasses. It felt like watching a movie instead of a trip to Universal Studios. I still think 3D has potential. The scene at the beginning where Jake Sully floats around the inside of the space ship is a theater experience I'll never forget, and the 3D pulled me into the moment. Oddly enough, the other 3D shot I really enjoyed was one where Sully was just laying inside the Avatar link. The claustrophobia felt more pronounced.
Think of it this way. Watch a badly colorized version of a black and white film. The color actually takes away from the mood. Then watch a film that's colorized well, and the added element adds a new layer of emotion. I feel like 3D is the same way. If it's just there, it's just distracting. But if it's used to add another layer of emotion, then it serves a purpose... And is also a huge film making challenge. Some of the angles in Avatar are very standard. By itself, nothing is wrong with this. An epic film requires naturally familiar elements, and Cameron knows how to add a little spice to even the most basic angle. In 2D, it looks amazing. In 3D, it just feels like a dull shot, because there's nothing set up in the angle that makes the extra 3D element interesting.
Plus, Hollywood studios are almost trying to run it into the ground. I understand not every 3D film will look amazing, thems the breaks of a new technology. But most of the 3D conversions seem outright incompetent. I saw The Last Airbender and felt miserable. I took the glasses off for a moment a couple times to rest my eyes*, and I couldn't see any difference in half the shots, but the screen looked like a bootleg of the film, even though I was watching it in the theater.
Possible irony to all this - All of my roommates want to watch Jackass 3-D, and I don't think anything is stopping me from going with them. But then again with the irony, I can't think of a film released in 3D more suited for the medium. I don't know what that says or means about anything.
*I took my glasses off 2-4 times during TLA and my eyes really hurt. My eyes felt a bit weird during Cameron's Avatar, but I only took the glasses off 1-3 times over the course of 2.5 hours, as opposed to Shyamalan's movie which is only 1.5. I have a feeling the quality of the 3D influences how it feels to look at.