My wife loves her asshole licked, especially when her pussy is filled with several fingers or a thick dildo. When she's on top, a finger in her ass pushes her to orgasm without fail.
My wife really like a deep tongue in her ass and when we do sex she always want a couple of fingers in her ass...she become so wet even in her ass that i feel is another pussy.
I love the sensation of a man's tongue in my ass. It's really nice to have a guy do that just before he pushes his dick into it. If he keeps his tongue wet enough, it helps with the penetration (although babyoil is also needed after a short time). So my answer to your question? I love it - feels wonderful.