We just got back and we did the Fantasmic Dinner Package at the Brown Derby last week. I booked this 7 days in advance. The Fantasmic show started at 7:30 pm and the latest PS time they would allow was 5:00 pm. It appears they are adding lots of safety margin.
We had a 4:40 pm PS and we were seated 15 minutes late (4:55). We didn't leave the restaurant until 6:25 pm. Things just seemed to move a little slow, but we weren't in any hurry (no complaints).
We were a little surprised at how long it took to complete the meal and I now understand why they have such early seating times. If you want better seats for the Fantasmic show, arrive 45 minutes before the starting time (yes, even with the Fantasmic Dinner Package).
Troy