This is really popular in Roguelike games like Nethack and ADOM. ADOM in particular could let you get a bunch of fun things by eating corpses. My favorite was the Kobold Shaman, which would cause debilitating sickness but boost your Mana score by 1. Certain creatures, like Dark Orcs and Giants were valuable targets because their corpses could boost your Strength. Blink Dogs gave you Teleport Control, and Pixies gave you Teleportitis. Eating the corpses of creatures corrupted by Chaos would corrupt you as well, but some of them, especially the bosses of the game, would give you /insane/ boosts. And of course, certain corpses gave you elemental resistances, which were really important.
I'm personally a fan of the idea that eating the brain/neural tissue of a psionic creature also gives you psionics.
One possible issue is that you're going to have your PCs hunting down specific creatures to get boosts. Might not work in say, D&D unless you use incremental boosts, but definitely something I'd like to see in more games.