These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: One Piece Film: Z
Decoy Protagonist: Some fans view the Straw Hats' role as this, seeing how a suprising amount of focus is on Z, whether he is onscreen or not. Most of the people who believe this consider it to be a good thing though, as it is a nice change from the manga's standard formula, and gives A Day in the Limelight to a villain who deserved to be canon.
Love It or Hate It: Not the movie, but Avril Lavigne's songs. There's fans who hate them and think it doesn't fit One Piece at all, fans who like the idea and consider it original, and fans who love the songs.
Take a Third Option: And there are those who were just fine with the songs...in the original form.
Moe: Nami and Chopper as children are absolutely adorable, and 18-year old Robin is also very cute.