Long time lurker here but thought I'd go ahead and give my experience with this today, just in case it helps anyone else. I had a 12pm-2pm slot. I lined up right around 10:40; the line was starting to wrap around Island Mercantile. Right at 11am they let us in. As we walked up, we were handed a paper FP for Flight of Passage. I had a 11:15-11:30 time slot. I took a few pictures as I walked in (and marveled at everything because MAN is it incredible!), but I walked right up to the FP line exactly at 11:15.
I made it completely through the full preshow when we were stopped. Cast members stated that they were taking it down in between rides to keep everything running smoothly and to make sure that you were "properly connecting" with your Avatar. We were stuck in that chamber for about 10 minutes before being shuffled back out in the grouping area. It took maybe another 10 minutes before we were put in a different chamber and had to do the preshow all over again. Everyone in my group was pretty entertained by this.
The ride is absolutely incredible! It's like Soarin' on steroids. I'm fairly certain I had my mouth open in awe for about 3/4 of the ride.
Definitely eat at Satu'li Canteen! I greatly enjoyed the meal I had there.
I don't believe everyone in the 12-2 slot ended up with a FP for FoP. They were just about out of the paper FP's when I made it up there. I say you most certainly need to be in line a good 90 minutes before your actual time slot, if not more, especially during this first week. As I stated, they let us in exactly at 11, so we actually had 3 hours to explore. It worked out well as I ended up spending a little over an hour waiting to ride FoP, which was more than worth it!