My nipples are sensitive, but usually it neither adds to- or detracts from the experience. It's just ''meh''. I got my left nipple pierced many years ago and now it's more sensitive, but I'm still not that much into getting it stimulated. However, I love it when a partner plays with either of them (pierced or non-pierced) when I'm close to having an orgasm.
As others have said, it can take a long time to heal. If you really want to get your nipples pierced, this is worth the trouble! Once fully healed, using cocnut oil will keep it clean, moisturized and give a slight coconut smell.