Indiana Jones Epic Stunt Spectacular is a major attraction as Indiana Jones appeals to a wide audience. If my mother looks forward to this, then you know people are going to want to go see it. As such, it has a large capacity, which is usually filled, so you'll need good timing to see this.
My advice is see the Indiana Jones Epic Stunt Spectacular in the morning or just see the last show of the day. Disney lists Indiana Jones Epic Stunt Spectacular as a FASTPASS attraction, but they do not use FASTPASS anymore. If you're in the queue area, you've made the next show.
Once you're seated, there is an opportunity to be used as an extra. It looks fun, although, be prepared to be poked fun at. If you're at all interested, when they ask for volunteers, you'll need to jump up and down, do somersaults and carry a bright neon light with you to get picked. In otherwords, if a 747 can't see you, neither will the people who pick. They like lots of energy and enthusiasm. The show itself is really fun, although there are times it drags on, especially when the crew is setting up the next scene and you just want to see the scene, not be lectured on how to be punched in the face. All in all, Indiana Jones Epic Stunt Spectacular is very exciting and fun.