IF you are going to do this, then definitely use FP. It is one of the slowest moving lines in all of Disney.
We have done it several times and really enjoy it. It's definitely doing at least once to see the special effects.
After reading this board, we used a FP for it last October after Wishes and actually had to wait around for a few minutes while they got enough other walk-up people to actually hold the show. So, a FP is not always necessary depending on the time of day you try to go.
