I think they said it is a hole different way of playing, but then again that could mean anything.
The way Todd described it (The sun affects you differently depending upon how much you feed, you can only feed on sleeping NPCs, etc), it sounds almost exactly like it was in Oblivion.
If Vampirism is more or less identical to Oblivion the first mod I'll make is one that turns it upside down.
Feeding should make you stronger and give a measure of protection to the sun whilst not feeding should svck in every way, making you much weaker without any advantages (indeed weaker than if you were not a Vampire at all).
I'll expand on this last but the first iteration will hit Nexus within 24 hours of the toolset being released.
The whole reason for Vampires getting stronger when they don't feed, is that drinking fresh blood, actually suppresses their Vampirism. Suppressing their Vampirism causes them to retain a more or less mortal appearance (Allowing them to blend into mortal society), but it also suppresses their supernatural strength/powers. Allowing their Vampirism to progress however (By not feeding), has the opposite effect. They gain more strength and powers as they become more a undead creature, and less a mortal man, but they also become more undead in appearance, making it plain for society to see what they are.
Vampires who frequently feed, are basically attempting to cling to their former, mortal life. While Vampires who forgo feeding, are embracing their undead nature. Do note however, that after a few centuries of being a Vampire, regardless if they regularly fed or didn't feed, their Vampirism will progress to such a state that it can no longer be suppressed by fresh blood. Vicente Valtieri was one such Vampire.
Another thing, that Ice Shout ability that they showed quite a bit of, looks like it would fit perfectly as a Power for the Volkihar Vampires, considering "I told him about the most powerful tribe, the Volkihar, paranoid and cruel, whose very breath could freeze their victims' blood in the veins."