http://video.google.com/videoplay?do...urning+crusade shows a couple [scarcely] populated areas of Karazhan, including Alliance vs Horde units on the Chessboard.
Personally I think Karazhan and the rest of Burning Crusade are a huge step forward for WoW and MMOs in general. It all looks epic, gorgeous, and interesting. I had my doubts about WoW's future when the old team left for Red, but this has put me at ease. Again, Karazhan is simply amazing looking, however I feel like the scale might have been a little off. There was a body on the ground about half way through the video and it didn't look in proportion with the player character.