No, don't watch it. It's a bad idea.
One Piece has horrible art. The girls have very big boobs and thin waists, and some guys don't look human. Heck, some of them look like fish! Oda doesn't know how to draw, clearly.
One Piece is so slow! Why does Oda bother with other characters? Look at Kishimoto, he only focuses on certain characters because the other people are clearly fodder! Shirahoshi? Who's that? Sounds like fodder to me!
One Piece is boring! It doesn't have lasers early on, and the Gum Gum Fruit sounds really stupid. Who wants a rubber power when there are much cooler ones, like the Rasengan, Sharingan, or Yoosookei's Spirit Gun from Yu Yu Hakachu.
One Piece has so many plot holes! I mean, if One Piece treasure location is already known, why aren't the pirates going after it? It doesn't make sense! Also, the power levels suck. Why is a Vice-Admiral so far from Admiral Level? Why is a Shichibukai powerful when there are some people who aren't Shichibukai Level in there? DBZ sooo much better, they have scouters. Oda is useless, he introduces Douriki but doesn't use it.
One Piece is so predictable! Here's the formula: land at island, discover a problem, kick bad guy's ass, and leave! So boring you know! Unlike my mature anime Darker Than Black, Death Note, Green Blood, and Tower of God.
One Piece is for kids! It's so childish! Look at Luffy, he's supposed to be 19 but acts like an 8 year old! Also, nobody dies in One Piece! So childish! Look at Bleach! Ichigo's mom died in the early chapters! Look at Naruto! Has something in One Piece come close to Jiraiya and Itachi's deaths? No, they all pale in comparison! OP is a happy-go-lucky manga, not for mature people like us.
One Piece is so long! It has 707 chapters and counting! Shorter series are better! Look at Gurren Lagann, better epicness in 26 episodes! One Piece can't compare to that.
One Piece has the worst drawn girls ever. Hiro Mashima of Fairy Tail draws better. You're better off reading Fairy Tail, because the main character doesn't ignore the rules of his own universe and is always fired up! Fired up is better than "I wanna be Pirate King", so obnoxious.
There are so many reasons why you shouldn't watch One Piece.