I'd say One Piece is best described as a very guilty pleasure. It's one of those shows that you either love or hate. Personally, I never really got into it, mainly because I can't stand the main character. I think there were about three routes they could've taken with Luffy, and they picked the worst possible one. Give a wannabe pirate the wardrobe of Huckleberry Finn and the powers of Mr. Fantastic. I'm not making this up. I've watched episodes, both old and new, English dubbed and Japanese with subtitles and even read some of the manga, and it's equally ridiculous in every medium.
Ultimately, it boils down to being a guilty pleasure Anime. If you liked it from the start, then you'll probably stick with it. It's like one of those sitcoms where you know it isn't that great, but you've been with it since the beginning and you've just gotta see it through to the end. Kind of like the new Battlestar Galactica series, or God help you, Naruto. If you don't get into it, there are other Animes out there that are way better, such as Fullmetal Alchemist and Death Note.
