A video of the first mission has been leaked.
Whilst graphically it looks excellent (I think the footage is from the xbox going by the reload commands) I can't say I'm at all impressed by the linear run and gun gameplay.
Seems to me that every Call of Duty game since the first has lost that sense of being one soldier in a war and not John Rambo. This just looks like lightweight arcade nonsense. I'll probably buy it but I'm far more excited about the new Operation Flashpoint.