Very bad quality video with some arena games.
What’s interesting is the voice-over (which sounds official — or, at least, sounds a lot like one of the Blizzard developers whose name escapes me at the moment): Apparently, in PvP, some talents will change to be more PvP focused. This is exactly what Guild Wars do, so they can balance PvP and PvE independently.
Also, it seems PvP will be more about counters. I just hope that, in Diablo, Blizzard doesn’t think “counter” as “interrupt”, like they did in World of Warcraft.