We just did the show and dinner package 2 nights ago. Fixed price of $36.95 per adult at the Brown Derby, and we got to choose items off the menu that totalled well above that price. The other restaurants that offer dinner package are not as expensive.
We got to the theater at 6:30 PM for the 7:00 PM show. The reserved section was maybe 50% full. I would say that the other non-reserved seating sections were filled 95%, with the only visible seats left well, well off to the side.. To get the equivalent seats that we had in the non-reserved you would have to have gotten there at least an hour before we did (my estimate).
So if you are going to eat dinner and you want to see the show, it's a real time saver. We easily spent an extra hour in the park instead of sitting in a seat, and with 3 kids ages 9, 7, 3, that was time WELL SPENT!
If you get the better of the reserved seats (which means you are closest to center), the seats are fine. This is coming from someone who only buys local concert/show tickets from ticket scalpers companies (at tremedously high premiums) so that we can sit in the first few rows for stage shows, as otherwise my wife can't see the show well. She was fine with the seats for Fantasmic. Again, just an opinion. You have to judge your own personal situation as to whether to do the dinner package or go earlier to get an equivalent seat.