Blizzard has posted the Black Soulstone cinematic which premiered during the Blizzcon 2011 opening ceremony. As Chris Metzen said, this version is slightly edited (to remove some story details) from that which we’ll see in the game. It’s got story info galore as it is, with Leah facing Azmodan in some sort of dream/vision/nightmare, where the Lesser Evil shares his plans for global domination.
That aside, the visuals are fantastic, so just enjoy.
I took a bunch of screens from the video on HQ, if you want closer/longer looks. Three thumbs below; see the new Black Soulstone Gallery for many more.