It's one of the longest attractions at WDW; I timed the whole thing once from the beginning of the doors opening for the preshow until we got of: nearly 40 minutes. It's a great "resting" ride.
The animatronic dinosaurs are actually tableau scenes from Fantasia. If you've seen the movie, you will recognize the scenes. The last rehab inserted an animatronic of EG, plus some voiceover into it, but it's still Fantasia's dinos. For the best close-up view of the animatronics, sit on the far right-hand side of any of the 3 cars; they all pull out in single file, and the largest dinosaurs are on the right as you pass through.