I leave for three days and there's like a million posts! Okay... maybe not that many... but you know. :-P
I don't think the AK curse is actually a killing curse. It's really a soul stealing curse. And Death Eaters? They just like to run around and collect souls for their Soulemon Tournaments every weekend. Voldemort is actually the Soulemon Master. He has the largest collection after all.
This also explains why they get along so well with Dementors.
[Susan, make me an icon about this and I will love you forever plus some]