behind the castle is the best the fireworks that shoot closest to the castle were so close and some of them went off right above me and the big ones that I still cant figure out where there coming from are so close. To me thats the most amazing spot ever. I was amazed all over again.
Oh, I recently saw them from Astro Orbiter, also pretty cool.
I actually don't like the Mainstreet Station. Tried it once and I thought the fact that the lights stay on and are so bright ruined it a bit for me. Comfortable spot with a good view, though.
While a lot of people go to California Grill to watch the fireworks, I think Ohana @ Poly has a much better view.
Inside the park I would say the best view is up closer to the castle near the entrance to Tomorrowland. You get a better view of Tink when she flies by
Tomorrowland Bridge
We did just try the area directly in front of the castle and it was too close. The castle ended up blocking a good amount of the show.
For something different we (usually we watch from the Tomorrowland section of the hub) watched from the Noodle Station. Wife didn't like it much (she prefers the hub, but that night was just plain crowded), but it really wasn't bad at all.