I've always had erotic sensation and I've always thought it was great, but I've already lost some due to binding. I also find myself very annoyed with the sensation if it's cause by non-sexual things (like if my binder is off and I brush against something). It's actually highly irritating in those situations.
Aside from that, I think it's a fair trade to lose sensation for surgery if it comes to that. I'm not worried about it though because I'll be doing something similar to keyhole. All I hope for is a good areola size and it'd be nice to lose some, but not all sensation.