One minor complaint is that sometimes things happen off screen that I would have really enjoyed seeing. I know, for the sake of saving space, that some things must be sacrificed but there are still some encounters that really stick out that I wish I could have seen. Most recently Zoro v. Neptune would have been cool. Here is a more classic example. Sanji v. Enel.
http://www.mangareader.net/103-2366-18/one-piece/chapter-259.html
^^ oh yea, it looks like our foul mouth friend instigated a fight with a god. What I find interesting about this encounter is here…
http://www.mangareader.net/103-2366-17/one-piece/chapter-259.html
…we can clearly see Sanji wearing shoes with rubber soles and, as any mook knows, Sanji's primary form of combative attack is kicking. Maybe this is just me daydreaming but I would have loved to see Sanji get at least one good kick in before he got fried (though I supposed that bit of foreshadowing would have ruined the surpise for anyone who didn't think that Luffy might have an advantage because of his rubber ability.)
Another minor annoyance, and I know it has been said a million times, I really wish some people would die. Specifically in Skypiea and at Enel's hand (I don't mean nameless fodder). It just undermines a villains ability when, at the end of the arc, all of the people that he attacked with freaking lightning start coming back from the dead just because. I know this is One Piece and it's not about people dying but couldn't Oda at least have sacraficed Pagaya or something?