I avoided seeing Avatar, because to be honest the trailer didn't impress me all that much. I became interested in the story line from what friends who had seen it shared, however, and decided to give it a go.
The 3D is subtle, free of gimmicky objects jumping out at the screen. It's a real, organic experience that made me feel like I wasn't even sitting in a movie, but witnessing the story through my own eyes.
Overall, the story is solid, timely, and one that has been repeated countless times throughout human history outside of a sci fi setting. At times I really felt connected with the characters, even though many were huge blue cat like creatures.