I like this Design article. There are differences between demons and devils again. The lines had been blurring for a while. This reorganizes and delineates what is DEVIL and what is DEMON. There are strong ties to the Temple of Elemental Evil in the 4E fluff. We have Tharizdun, the abyss in the Elemental Tempest, and there is a reference to Imix in a DDM article. The cosmology article that will out on Wednesday will clear up some more things.
I think alignment is gone as we knew it. Was it Andy Collin's blog that said:
"Do you think you know what the word Chaotic means? Really? Are you sure? Care to place a wager?"
Demons serve to bring about entropy through evil. Either with their bare claws or through sowing the seeds of destruction in mortal realms, i.e. plague, famine and war. The order of the world is reduced to the chaos-that-came-before.
Devils want to subvert the order of the world for their own purpose. They twist whatever they interact with, but the form stays the same.
Chaotic is much more active in this fluff. It is a cancer in creation. Tharizdun is chained but the seed of evil, that rent a hole in the Elemental Tempest itself, still creates twisted abominations. Is Chaotic the new evil? Is chaotic the Lovecraftian form of anti-reality or proto-reality? If the abyss is a hole in the Elemental Tempest, where does that corrupting hole go?