What were your reactions to this quest, and are there any others that you find equally or more so messed up?
I loved the quest. I did find it very disturbing. I am role-playing a character who is a very conservative Dunmer Daedra-worshiper, so it was weird to see how far down the path of - well - sheer evil the quest took him. Basically he will do anything to please the Daedric Princes, so I went all the way and he's a somewhat reluctant member of the coven now. Really he still thinks cannibalism is pretty gross, but doing repulsive stuff is what Namira is all about. He gave the ring to Eola, and they are currently traveling companions. OK, OK, I admit it, I have a crush on her.
I do wish there was a way to be a cannibal without becoming a freaky cultist. It's just another day at the office for any Bosmer. But I made a whole thread for that http://www.gamesas.com/index.php?/topic/1292520-cannibalism/.

The Molag Bal quest (also in Markath) is almost as disturbing, but not quite. The victim there is a real jerk to you, so it's a little easier to torture and murder him. But not much.
I also did the Vaermina quest somewhere near Winterhold. Not that disturbing, although not very nice either.