Also just seen it, Not sure what to think of it. It feels like a 90 minute recap for viewers who've already seen it. If you want to watch it like that it's fine. If people want to skip the arc and replace it with this, or watch this as a standalone movie while not being familiar with One Piece, this won't hold up. So many things got lost and cut in this.
If you want to re-experience Skypiea in higher quality in 90 minutes this is 9/10
If you want to use this to skip episodes when you're new to the anime this is 4/10, can't be done in 90 minutes
.The only new character was a random brunette even that in the ending song. What now?
I was surprised by that too, have no clue who that was. Looked super genric as well and she didn't show up in the special either. Is it like a Marvelesque after credits set-up for the next special, did some girl won a contest to get added to the OP opening ? I don't know.
EDIT: I found an answer:
it's Namie Amuro, who sing One Piece opening at recent anime (title "Hope").
Soon she will retired from entertainment world. That's short special animation about One Piece x Namie Amuro