IGN has a quick look at the new Beast Mode in GOW3. You can play as any kind of enemy unit now (well, except for Brumaks). All I can say is "wow". This is gonna make multiplayer insanely fun (that is, until people find all the hacks and ruin it).
I cannot express how excited I am to play this game. I love the series, and I'm dying the play the third and final chapter. This new mode might be the thing to bring me back to the series' mutiplayer, as cheating has become widespread across it's predecessors.
Check out the video here: http://www.youtube.com/watch?v=k86rf5osUWY