We were there last spring, and used our FP on Flight of Passage. The standby line for Na'vi River was 60 minutes. We have noted in the past that the standby lines sometimes move faster than the listed time, so figured we would give it a shot. At first, the line was moving quite well. We noticed that the line operator would let in a bunch of fast pass people, and then let in a bunch of standby people, and all was going smoothly. When we got to the middle of the standby cue, the ride broke down... it took about 15 minutes for it to start up again. In that time, the line operator had changed. The new one was letting just fast pass people in, and then one or two standby people every 10 to 15 minutes, even if there was not a line of fast pass people. After waiting in one spot for close to 45 minutes, we called it quits and left the line. If you get a good line controller, they can manage both lines well, if not, then forget it.
In my opinion, the standby line is not one of the better themed lines for passing time. There isn't a lot to keep you occupied in line.