Your friend is probably confusing the fact that he loves it with calling it tasty. It's going to taste like skin, for the most part.

I do not taste anything at all.  "Sucking" may actually be annoying/painful to her.  Women are different in their sensation.  Nipples on both M & F/M are erogenous zones.  My partners seem to enjoy a variety of gentle lip & tongue techniques on their nipples...  and I enjoy turning them on, guided by their cues.  I have brought women right to the brink by this alone.
skb

pop tarts...

This post reminds me of a Mitch Fatel joke where he ponders how awesome it would be if a woman could lactate all the time.  My favorite line is when he says "I'm thirsty.  Which one's chocolate?"

In all seriousness, nipples don't taste really like anything unless a woman puts something on them or has some sort of perfume/lotion.  Pussy, on the other hand, can have subtle to very strong tastes depending on the woman.  I think your friend is taking a bit of poetic licensing when he talks about his nipple flavor of the month.  It's a nipple.  Not Baskin Robbins.  I like sucking on nipples because it makes me hot n horny, and in many cases it can for the woman as well.  Careful though, some women don't like their nipples sucked or have times where they are too sensitive.  Always go light before turning your mouth into a nipple Hoover-Vac.

See you later, alligator...

If you have to ask, you don't either don't understand, or are playing us.  Either way, I have nothing left to say...