Its funny. The two arcs that get the most hate, Skypeia and Fishman Island, contain some of the series most important plot points.
I personally love Skypiea, but hate Fishman Island with a passion. It only really becomes plot relevant in the final few chapters of the arc, I might buy the set that covers those episodes, but all of the stuff in between that was painful for me to read the first time around. I thought if I read the chapters back to back I might get more joy out of them, so a while back I bought viz's release of Fishman Island and read the chapters in one go and I still hated it all. lol
! Aside from the Jinbie and Shyarly stuff. I loved that, but it didn't make up for all the other stuff I didn't like.