I am a full on Avatar fan, so I got the story line as well, and I agree with Animatronic is incredible. But interestingly I don't think slowing it down would help, I'd think it would make it work. We were luck enough to have 2 preview appointments in may (One as AP holders, the other as DVC members) and we rode Na'vi several times. What I found is that it got worse every time. The first time I will admit the colours and the animatronic and the screened in characters (the Na'vi walking, the big cat things) were really impressive, but as we repeated our trips I noticed how 2 dimensional they screened characters were, and the fact that they were on short loop repeats. I really started at some specific pieces of the glowing fauna and, this is my honest view of it, realized it didn't look all that different than the black light props I remember being created in highschool, like really, if you stare at them, you will see there actually isn't a lot of detail in many of them. And then we looked at the section where the silhouettes along with the feet are cast on the leaves above you, and again, if you really just stare at them, it kind of looked cheap, not some marvel of imagineering at all, but like a little set of feet / body on an arm attached to a small machine that moves them in a predictable pattern.
The shaman, still blew my mind every single ride, its amazing. One of the coolest things I have seen, ever. But as for the rest of it, just doesn't impress me. Maybe its because it was so hyped I was really expecting a lot, or maybe its because I wanted it to be something so awesome and detailed and immersive ... or maybe it just doesn't work for me

Either way, Na'vi for me is only a little better than the hall of presidents, its neat and stuff, but its mostly a place to cool down if its hot out, and isn't really worth much of a wait.