As a butt eater, I only eat clean butts, like fresh out of the shower (preferably a co-op shower where I can wash the butt thoroughly myself). There are ways to clean deeper if you want to enter the cavity.

I've known some people who eat not-so-clean butts, or go ass-to-mouth, and it doesn't seem like the taste is pleasant; seems like the degradation of the bad taste is a part of it.