Well i am glad to say that there is exactly 24 hours until "Dawnguard" is officially released on the Xbox-Live Marketplace. I would like to go over any questions anyone has by giving all the know info at the time.
The "Dawnguard" DLC map will not only add 2 large NEW areas to the main "Skyrim" map, but also integrate areas into the current map allowing the player to continue exploring the large world.
There will be new skill trees for both the vampire and werewolf forms.
(Note that you are still unable to be both vampire and werewolf at the same time)
Both the vampire and "Dawnguard" HQs can be owned and used as homes in "TES:V Skyrim".
New items include: Dragon Bone weapons, (Including bows... crossbows unknown), crossbows, spells such as "Spectral Force" and the largely anticipated levitation spell seen at 8:40 in the video above, and much, much, more fancy new toys.
There will be new armor for both the vampire and the "Dawnguard" paths.
You have the ability to tame both the giant trolls seen at 6:59, and the supposed gargoyle seen at 6:31. Though not know yet, you may also be able to tame hell hounds.
For high level players, new "Legendary Dragons" will be added to the game to give a bit of challenge.
*SPOILER ALERT**SPOILER ALERT**SPOILER ALERT**SPOILER ALERT*
In the story, the vampires are attempting to permanently block out the sun using the "Elder Scroll" seen at 2:25 on the females back.
Vampires now have the ability to travel in sunlight and are given viles of blood to make up for feeding on NPCs (Though you are still able to feed on NPCs at free will).
The 2 red sigels on the map are those of "Markarth" in the bottom left, and "Solitude" in the top left. I speculate that this may be the general area of which the "Dawnguard" DLC takes place.
Players will journey back into a portion of "Oblivion" know as the "Soul Cairn".
Though that is all that is known at the moment, i will be back with more. In addition, if you have any more to add, E-Mail me at email@example.com