Lightsaber battling is serious stuff, and when you're Darth Vader — the second-most powerful Sith in all of the galaxy — you can't go pitying any pesky Jedi that try to get in your way.
The Stunt People folks wanted to show exactly what Darth Vader sees when he's slashing down enemies with his lightsaber or Force-choking them to death, so they strapped a GoPro Hero 3 to Darthy and captured the action from a first-person perspective. Halfway through the battle, the perspective shifts to the Jedi's point of view, which we presume is only fair.
For the lightsabers, the actors used modified Hasbro Ultimate FX lightsabers with the LED light strips removed and replaced with a single LED.
Stunt People promises more to come, but for now the first-person lightsaber battle preview will have to do.