I will echo a previous poster's experience that I felt like I spent a good deal of time with my face down in my phone screen, refreshing while we walked etc. We had a party of 6, and it was doubly difficult because I had to get our core party of 4 FP at 60 days, but the other 2 at about 25 days, and ended up having to take other attractions for them, and then try to match up ours after we'd used our first 3, etc. It was a lot to keep up with. When we got to Small World, I actually hadn't clicked on my name so I wasn't on the FP and then it wasn't available. The CM was understanding and did let me through, but she advised me to be more careful in the future about making sure my entire party was selected. I doubt a headline attraction would've been so easy.
I agree also that you should not let this replace your other opportunities to ride the headliners... rope drop, EMH, FP at 60 days, etc. On our recent trip we employed all of these tactics and rode every ride multiple times. The only ride we never got a FP for was Na'vi River Journey. But my husband and son got in line for FOP at 10:40 on an 11:00 park close night, and my daughter and I rode Na'vi 4x's straight through, they just let us stay on. It worked out as there was absolutely no line. (FOP still took an hour plus.)