As an alchemy ingredient, I find Daedra Hearts to be a bit of a disappointment. Alchemy in Oblivion in Generally quite excellent - there's a wide array of useful potions and poisons. But, Daedra Hearts are A) Heavy, and Only available by killing the tougher Daedra, like Daedroth (ok, they're relatively easy, to be fair), Dremora (who are pretty tough, and usually are either armored, or paralyze you, or absorb/reflect) and Xivilai (who are rather a PITA, because they summon Clannfears, and then absorb 80% of the spells you might throw at them).

So, you go through a few planes of Oblivion and you have a stack of 30 or 40 Hearts. What do you do with them? They are heavy (2 stone), meaning they will cause any resulting potions to be heavy, and the effects on them are fairly common and usually better using other, lighter, ingredients.

About the only thing I think they might be worthwhile for is, I saw on UESP there is a 5 or 6 effect poison that can be made with them, which I might try. Perhaps that makes their combo of effects worthwhile.

Just eat them as a health restorative.