I like piercings in general as long as a person doesn't go overboard with them (more than 6 piercings and I say it gets too cluttered looking), and I think a ring in the bellybutton doesn't look bad at all--however: Bellybutton piercings take a VERY long time to heal, and they're quite painful. I've had a number of friends that have had it done, and the area around it stays red for many many weeks, if not months. It's supposed to be at least as painful as nipple piercings, which I'm too chicken to get.
Myself, I went for the P.A. and the septum--the P.A. nobody sees unless, well, you know (and it's probably the quickest healing piercing out there), and while a septum piercing is healing, you can wear a retainer that nobody sees (looks like a horseshoe that flips up inside your nose), and if you decide you don't like it and take it out, nobody knows you ever had one. The bellybutton piercing I suppose is the same way in the sense that you can't tell it was there once you take it out, but man oh man, the pain that a bellybutton piercing causes a person to endure.
If you really want to go for it, then do it. I think it's great when people go for what they like, but be aware that it's very painful and takes a long time to heal.