I hope the 'evil' faction will have some lore backing aside from the stereotypical 'evil and hate the sun' that vampires get.
More specifically, I'd like to see the Dawnguard being Stendarr worshippers and the evil faction to be Molag Bal cultists.
This.. I really, really hope there is strong lore for this one as well... It's one of the reasons many people, especially long time players of TES, love TES.
It will be insanely dissapointing if it's just a stereotypical evil vs good thing...
Even more depressing is if the quests are like the Thieves guild........... Do 57349857983457x generic side quests to unlock a proper quest.....