I haven't read everything in the thread but, did anyone else noticed how this fallen angel concept is similar to that Demon game from White Wolf's World of Darkness? I didnt get to play it, but as far as I know, Lucifer had offered the apple to Adam and Eve, who were basicaly animals, in order to awaken them, so they could realize and appreciate God's creation (there was a passage that made me laugh, about how the angels arranged a simphony, but the man and the woman didnt care about it, and went away looking for food). Then God spoke and cursed Lucifer and his lot, imprisioning them. The game focuses a lot on True Names - wich is one of the ways to summon/control a fallen angel away from its prison. On that setting, not every demon is evil, but being forsaken by God made most of them that way.
Ok, D&D has devils and demons, but even in the article we hear about how they both originated from the same real world myth. Either way, I've always thought of devils and demons that way, but I wasn't surprised with their roles as much as I was with the intention to make them clearer - that's really nice!
And there's another thing in the article that made me think about WoD: the Abbyss being described as a burned hole in the very structure of the plane, tainting those who come near, and this "Elemental Tempest". In 'Mage: the Ascension' there was an Avatar Storm, the Maelstrom, some sort of hurricane of fragmented souls and spirit shards, that was pratically ripping the cosmos apart (you know, 'end of the world' stuff). I know there isnt much to compare here, but made me go back to my Mage Campaign... good times, good times :\