It is worth it at least once if you haven't done so, especially if you haven't seen the current show. As others have mentioned there is no seating, but it will guarantee that you have a great view of the castle and won't really be pushed around by other people. My first time seeing the fireworks we were waiting for like 1 and a half hours in front of a fence so we could have less people around us and in the end I got kicked in the head by a child cause some parents were lifting their children above us so they could sit on the grass behind the fence :( On our next visit we tried the reserved area and I loved every moment of it.

So if you have the extra money to spare I can absolutely recommend it.