OK, before I get into this I want to know if you're talking about the US dubbed version that was butchered by 4Kids TV and CN. If thats the case than YES, its quite horrible. They havent put in much effort in casting nor editing as they did in Naruto. But you must admit that story wise "ONE PIECE" is solid and the artwork isnt something to be overlooked either. I'd like to say the music isnt bad either but...the US attempt to translate the original OP+ED songs were...ugh. Other than that...its horrible. The editing they've done is just...unspeakable. They've edited out a lot of good action along with a great amount of blood. Xd The US cast isnt horrible overall...really the only character that I have a problem is Luffy. The rest of the crew members' VAs arent that bad.
Now IF you were referring to "ONE PIECE" overall including the original JP and saying that it sucks than well...I dont know what you're talking about. It's obviously going strong with nearly 400 episodes (Its been on air for nearly 8 frikkin years!!) so...yeah, kinda self explanatory.