I've wondered about this, as well. Previously, I had my nipples pierced in the hopes that it would allow me to feel something in my nipples and it... kind of worked. I still didn't feel much, there, but it was a tiny improvement. I took the piercings out a couple months ago so that they'd have a chance to close up before top surgery.
However, I do like the aesthetics of pierced male nipples, and since I'll be getting free-grafts, maybe it'll allow me to get some sensation there once I'm healed up. Hm.