We just came back from seeing the 3-D version of it a couple of hours ago. It was awesome. James Cameron created a whole world and alien culture that was entirely believable. Absolutely amazing!!!
As to the messages, here's a brief synopsis of the plot. Humans have basically destroyed our own planet. Now, we have found a resource on the alien planet of Pandora that we want. Unfortunately, the aliens are living right on top of this precious resource. You can draw similarities to the current Iraq situation, where many believe we are there for oil. You can draw parallels to the American Indian, who we slaughtered for their land. The movie shows how horrifying these actions can be. It definitely sends an environmental message about taking care of our land and natural resources. I thought the messages were placed nicely in the film and helped to enhance the story. I personally enjoy movies like this, rather than mindless "Transformers type movies".