With all the awesome effects I was worried that the story might have floated off like one of the mountains in the movie -- however Cameron knocks it out of the park by providing a solid and emotionally compelling story that touches on humanity and forgiveness over greed and destruction.
The technology allowing the actors to transfer their performance to their synthetic counterparts is amazing. In that respect, this movie reminded me of Jurassic Park -- on one level you're talking about genetically engineering dinosaurs -- but on another, they really created compelling animated dinosaurs!
Well, in the same way, Avatar shows people transferring consciousness to synthetic alien/human hybrids, but on another level, Cameron really developed the technology to transfer the actor's "consciousness" -- their performance to the CGI models. Like Jurassic Park, that's nothing short of amazing.