Army of Two: The 40th Day "Pushes Co-Op Design Forward"
The original Army of Two did a lot right as far as co-op is concerned. All signs point to this trend continuing in the sequel, Army of Two: The 40th Day. In fact, according to Kotaku, The 40th Day compares very favorably to other co-op all-stars such as Gears of War and Resident Evil 5. Their hands on preview is definitely worth a read, particularly these snippets about innovations in co-op.