People in the rainforest eat goliath tarantulas as a delicacy. They barbecue them. I hear they're quite tasty, although I've never tried one. I have done the live octopus thing though (too chewy, but tastes alright), and I've eaten grasshoppers (tastes just like popcorn). People can and do eat almost anything edible, all over the world.
Eating sentient animals may be a problem, if the brains are ingested. Eating brains causes prion disease, similar to Mad Cow. Simply eating the flesh of a sentient animal, I don't know. Pretty gross though.
I'd also suggest a Will save to eat something weird, followed by a Fortitude save if the Will save is failed. Fail the Fort save, you vomit -- not only do you not receive any sustenance, but I'd probably also nail the poor sucker with a point or two non-lethal damage. If you manage to successfully eat something disturbing, you'd probably not have to roll a saving throw next time you eat that monster, or you'd get a bonus to the throw at least. Characters that routinely eat their victims, like werewolves, would get bigger bonuses to their saves, and would often not have to save at all. At least that's how I'd rule it.