Considering Oda's supposed contribution to this movie, it was pretty disappointing. Note that Shiki's abilities and some other things are spoiled in this review just since it's hard to talk about the movie without spoiling it, but... ah, who cares? The movie was predictable, anyway.
I simply couldn't think of the story as being more than filler. I know they tried to make it "tie into" the main story, but I simply wasn't convinced. They added this magical "Shiki" character who escaped Impel Down! That place has such tight security that NOBODY HAS EVER broken into or out of it until Luffy managed to. Oh... wait, there was that one other guy who did it, how could we forget? What's more, he was Gol D. Roger's hugest rival and controlled a fleet of incredible proportions. What's even more, the news of his escape from Impel Down was broadcast to the entire world in the newspaper headlines, so EVERYBODY KNOWS ABOUT THIS GUY, and yet... he doesn't exist. He also destroyed Marineford before... He's like a hollow copy of Luffy's accomplishments for the sake of seeming like such a worthless character can be Luffy's rival. He's never mentioned in One Piece because he's nothing more than a character hastily inserted into the anime series in some weak attempt to create substance for the movie.
But okay, let's move on, shall we? This guy's been doing big things like making islands float and rampaging around East Blue (which shall hereby be forgotten by everyone). This is really quite horrible, so the Straw Hat Pirates decide to put their great adventure on hold. That's right, they're going to quickly sail back to where they started so they can save East Blue. That would surely take WEEKS or MONTHS, but don't worry! They'll surely make it back in time to save their hometowns. And they'll find some way to go back up the Reverse Mountain. Hey, I guess Brook can say hi to Laboon, going against his promise to circumnavigate the globe to see Laboon again. Seriously, the story was shit. It wasn't planned out at all and does NOT tie in with the main story in any way at all. By the way, this is only the introduction to set the stage; the movie's barely begun.
To me, it felt like the movie was trying very hard to be like "One Piece". The comedy was just pretty typical and didn't make me laugh. The "YOU CAN TALK?!" joke didn't really make sense seeing as everyone knows the guy can talk, though I found it slightly amusing. The final stage of that running gag was pretty decent, but overall I think it was a bad idea to try and stick a running gag into a single movie. There just isn't enough time to make the viewers familiar with it unless you throw it in their faces at every opportunity like they did in this movie. The bird and the electrocution humour felt like a copy of Pikachu from Pokemon.
The characters were... in character. Their costumes for the movie were fan service. They looked cool, there's no denying that. Shiki and his crew were made up entirely of complete morons. They also felt like a forced attempt to emulate "One Piece" - the three main villains were given very blatant quirks. One Piece often does a good job of making each character unique, like how Don Flamingo is always laughing and scheming, how Jinbei is honourable and self-sacrificing, how Zoro can seem scary while actually being a really great guy. Shiki had a steering wheel in his head and his own special laugh, which just felt bland and made him look like a joke. His assistant's shoes made fart noises and he had his running gag; the fart noise thing just felt really, really stupid. The gorilla dressed oddly and seemed to have a King Kong mindset or something. The characters had no depth; there was nothing to them beyond the quirks.
Shiki's power was kinda nonsensical. I can accept the floating stuff, but his special moves just didn't relate to that at all. When the Straw Hats fight him, the results are just kinda typical... like they want us to think "Wow, Shiki is so amazing and is not a guy to be messed with". I could feel that way about God Enel, but Shiki did nothing to earn a reputation like that. He just did some move that made no sense and everyone was suddenly too slow to do anything. I can't accept that, even if Luffy was hungry.
After thinking about it all, I think I rated this movie too high. The only good One Piece movie is the one where Chopper joins their crew... But it isn't good because it's a movie, it's good because Oda actually wrote that story and it was really touching; it was touching in the series. All of the movies are mere merchandise created to generate more money by throwing the "One Piece" name all over the place. If you're an extremely hardcore fanboy or if you can't tell good anime from bad anime, then this is the movie for you. One Piece has a good story, but you should just stick to the manga if you're tired of fillers and empty movies like this one.