I have ridden this ride twice now, and it is the real deal. It is tough for me to give a lot more info as so much is already available online. The queue is second to none in my book. It is simply a work of Imagineering art, providing a story of its own starting in primitive caves, advancing through the military base that is slowly succumbing to nature. The animal sounds in this section are a nice touch. The science lab with the Avatar floating in a tube is incredible. We also liked all of the studies and lab tests that were happening.
The decontamination room is fun. We really enjoyed the "theater" of it all. This is where they really do a good job of explaining things for you so that prior knowledge of the film really is not necessary. The scene with Dr. Ogden is also informative, furthering the narrative of what is about to happen. I also think that these sections really demonstrate why this land works better in DAK as opposed to DHS. The Imagineers were crafty with how they work in concepts of conservation, endangered species, etc. This world simply "fits" better in DAK.
The link chairs help build tension as you can watch the information on your personal screen of your link chair. The part I loved was the chair vibrates as you get closer to starting the simulator. Then these bright lights flash in your face. When you look up you suddenly realize that the wall in front of you is gone. The same flashes of light appear in front of you. This effect is so well done it is freaky how you transition from looking at the screen on your link chair to the big screen in front of you.
The simulated ride is exhilarating. I find that to be the best adjective to describe it. I really felt like I was flying. The 3D is great, helping to pull you in the action even more. The dives are very well executed, and the lean of the chair coupled with the wind that hits your face creates an effective illusion, as does the water sprays in your face during various oceans scenes. The water scene itself is one of my favorites. The cave where you stop about half way through is a beautiful moment within the ride.
All in all it is a home run, providing thrills without producing a lot of motion sickness problems. It is one of the best attractions in all of Orlando. If I were asked I would rank it higher than Gringotts in DA.