We watched the Fireworks at MK for the first time during our last trip to the Fort (Nov/Dec 2016). It was nice. We could see most of it (but not as well on the lower stuff). You do miss "Some" of the show as you cannot see the video projected on the castle which kind of aligns with the fireworks, but it's still kind of nice, especially if you are concerned about not trying to jockey your way out or around the park at that time. I would recommend that you have seen the show at least ONCE at the castle so you get the full effect and then the view from the fort (or other remote locations) has a better meaning/understanding of what's going off and why..
Like NoM, I prefer the show at the castle, but I still don't like the crowding and staging an hour (or more) in advance to get a good location.