Story: The story is good, but a little basic. I don't want to give spoilers, but a town is being terrorized by marines, and in the story you get two flashbacks of the first episode of One Piece.
Art: The art is not as good as in the anime, it sometimes looks like the characters are flat. Also the faces look sometimes kind of weird.
Sound: The sound is just as good as always, especially at the end. At the end you here a song, that all of you know, and you will get really fired up.
Characters: The characters we also know from the anime are amazing. There are a few useless characters in the special. But you will love to see the progress Coby has made in the timeskip.
Enjoyment: You will enjoy yourself with this anime. The most important thing in this special, are of course the flashbacks. The flashbacks are really enjoyable, because they are not the same as in the anime. You will also learn how Luffy got the scar on his cheek