Battlefield: Bad Company 2's co-op mode, called Onslaught, is now available for purchase on Xbox Live and PlayStation Network. The $10 / 800 
add-on adds in a four player co-op mode on five maps - Valparaiso, Atacama Desert, Isla Inocentes and Nelson Bay.
The mode involves both infantry and vehicle based combat as players work together to complete objectives on each of the maps. We've got a launch trailer for the mode posted below.
Has anyone checked this out yet? What's the good word?