Back to tho Na'vi River Journey - why do people feel the need to be directly hit over the head with a "story"? Can't it just be beautiful for the sake of being beautiful?
I waited to explore Pandora until dusk/dark. It made for a very natural transition to get on this ride, which simply seemed to be a continuation of the exploration I was already doing, just on a boat instead of on foot. I think my jaw needed to be picked up off the floor of the boat. It was 100% pure eye candy, and I enjoyed it tremendously. I thought it was very well-executed. Sometimes rides with storylines can tend to be rushed with plot points, so it was nice to have a ride in which I could just soak in all the rich details.
Perhaps it is just because the time of day I visited, but I consider it to be an exploration of the richly-detailed Pandora land you are already in. It doesn't need a "story" - you are left to draw up a story, much the same as if one was to float down a river in their own land.
Creating something beautiful for beauty's sake isn't a bad thing, in my opinion.