According to the PlayStation Blog, there will be two versions of the demo to download: a 2D version and a 3D version, and the 2D version will support split-screen co-op. Both will take place on the "Icy Incursion" level.
Both demos will also support the PlayStation Move, which can be utilized to make "Brutal Melee" attacks. Players can thrust the Move at the screen to perform the move; the melee button on the controller will also perform the attack.