We were there on Friday May 16th. They were turning people away who didn't have a Priority Seating, so I'd highly recommend you have one, especially if you want to go on the weekend.
BTW, our meal at FF was simply outstanding. The best of the trip.
and remember a PS is not like a reservation it just means that you'll get the next available table ahead of walk-ins so there can still be a wait. Definately worth it even if you have to wait.