Sadly, the anime adaptations goes from good to great to amazing to ok to absolute clusterfuck. It's a really depressing case of unending anime series syndrome. I remember watching this about 7 years ago when there were about 400 epipsodes, and you could mostly skip all the filler arcs and end up with a kind of sluggish but overall enjoyable series, but later arcs, I believe starting at about episode 430-ish, have a lot more filler INSIDE the actual adaptation arcs, which makes it that much more difficult to get around. I've also seen some of the newer fights, and they were really disappointing. The animation was really bad compared to the better arcs (Enies Lobby, Thriller Bark and Shabaody Archipielago).
My recommendation for watching One Piece is: look for a guide that says which episodes are filler, and try to skip as much of it as possible. If it ever becomes unbearable, switch to the manga.
Personally, as soon as I caught up with the anime, I started reading the manga. I still read it to this day and it's on my top 3 manga list, alongside FMA and Magi.
