The crowd for the fireworks show was huge when we visited Magic Kingdom on a peak weekend. My friend insisted that we had to see the castle projections up close. Almost two hours before the fireworks show, we secured a "front row" unobstructed view of the castle in the area between the front pit at the foot of the castle stage and the Mickey and Walt Disney statue.
During the fireworks show, Disney cast members keep clear pathways that cut through the crowd. Position yourself on these marked pathways (marked by paint or tape), so that no one will stand in front of you - no tall park guests or guests holding their children on their shoulders will block your view.
Also - do not stand in the closed-in area directly in front of the castle. The area is too close to the front to enjoy the full panoramic view of the fireworks behind the castle. Even where we stood, it was too close to really appreciate the fireworks. My friend said the best place to view the fireworks show was near the Mickey - Walt Disney statue but on the day we visited, that area was full of projection and entertainment equipment.
Worst is that at around 1/2 hour before the fireworks show, the Disney cast members asked all of us to stand up - we watched everyone in the pit area being pushed forward to make room for the latecomers who stood behind them. So now guests who had staked their position 2-3 hours had a worse view of the castle and were packed even more tightly in that area.
The fireworks program really is an incredible show that was much more than just fireworks. Would we ever do this again? Probably not but if the fireworks show is on the top of your list, hopefully these tips might make the experience more enjoyable.