Watch one of the first Mesmer PvP videos at the Battle of Kyhlo.
Demo by ArenaNet showing off their PvP in The Battle of Khylo. It wasn't one of their big matches, but its extremely informative.
In the first reveal of player-versus-player content, we get to see a European guild, Boon Control, challenge the talented developers of Guild Wars 2, ArenaNet. The video mostly features an Elementalist played by a developer. Thanks to Wartower.de for this high quality video. There is also an interview with Boon Control members on PvP.
The final PAX 2011 developer tournament that was recorded. I believe that there were roughly 8 more matches that weren't streamed over the internet. Who knows, maybe one day we'll get to see them.