You're right that it's presented pretty vaguely. There's the new Demon Warrior class (which many claim in itself is worth getting the expansion); the NPC's starve and have a few other new interactions; lots more quests; the new environments are basically some new cave/dungeon/town textures; and several other things. In truth I've forgotten some of the new features.
Shadow probably should put out a much more detailed list on DW features especially with DC now on Steam and with the likelyhood of DW coming to Steam soon.
Stephen A. Hornback