If you were excited about Dawnguard, Skyrim's first piece of DLC, before, wait until you see it in action. The video shows you the vampire lord transformation and a ton of the skills that come with it, including summoning a gargoyle, using "vampiric grip" to lift enemies in the air, melee attacks and shooting energy balls. It also shows a bit of the Vampire Lord perk tree.
The video also shows off how crossbows work and a bit of the mounted combat.
Part two of the video confirms new shouts for the DLC. Watch it here: