I don't hate Viz at all. A lot of their works are fantastically done, with great editing and excellent translations. I find those a joy to read.
However, One Piece is not one of them. For starters, there's just something about the translations that bug the hell out of me. And really, that has nothing to do with knowing Japanese or not (I actually do, besides the point.). I just… Find it unpleasant to read. Often the lines just don't fit the feel of the story at all, and I find picture and text not to line up quite a few times when I'm reading the story.
Viz's liberty with insults and curses is a fine example. Call me crazy, but ''Darn you, you scurvy rat!'' just doesn't really impress me that much when I'm reading it.
Then there's the translated sound effects, which I absolutely loathe. Let it be noted I have nothing against translated sound effects in general, if they're done well. Which these aren't. They're sproingy, cartoony, and sometimes even make the actual image hardly readable.
Now, of course this is not always the case. Sometimes the translations are very well done and the sound effects don't always interrupt the joy of reading.
With a ''two volumes'' a year policy, though, as well as a price tag quite higher than those of the Japanese volumes…. I see little that justifies spending money on their volumes.
Considering the Japanese releases are pretty much flawless, and I read Japanese just as well... It's a pretty easy choice for me.