The fastpass thing is so funny. My son and I know how to maximize our usage of fastpasses, but there are some rides that it is just not necessary. I don't agree with the poster who said that its a waste for Indy. If you are lined up in the line outside, you will definitely be wishing for a fastpass. They used to have fastpasses on POTC - but that was really useless. Even if there is a rope line outside the attraction, it only takes at the MOST 20 minutes. Its a very fast loading ride. Haunted Mansion sometimes has fastpasses and sometimes doesn't. Its another one of those fast moving lines so for me that is just a waste. . .the line just doesn't take that long. Autopia is good for a fastpass if there are people weaving through the stadium portion of the line. Space Mountain, Big Thunder Mountain Railway, Roger Rabbit's Cartoon Spin, Splash Mountain, Soarin, and California Screamin are musts for fastpasses. Tower of Terror has fastpasses but the line moves relatively quickly so its really a personal choice. . .oh and the wait time on the gate always says 13 minutes at the minimum so even if its a 5 minute wait, the sign will say 13 minutes. Mulholland Madness is usually not too busy so not really necessary to get a fastpass. And Grizzly River Rapids has fastpass but the longest wait I have ever seen there is 20 minutes.
Hope that helps.