I've been thinking about doing this too, but I think it's better to leave it to the professionals... I'm a bit worried about the pain though. It hasn't been really bad (except the medusa piercing, I had water rolling down my eyes because it stang so much!) for me, quite the contrary in fact. But getting your nip pierced doesn't sound exactly like a very pleasant experience...
Oh yeah, I've heard from many people that it gets really swollen. I'm afraid that if I do get it pierced I'll choke on my own tongue while I'm sleeping or something.