Dead Nation's expansion pack, "Road of Devastation," is about to get a bit less devastating with the addition of the "Arcade" game mode. As the "Road of Devastation" was about surviving against impossible, zombie-filled odds, "Arcade" is about modifying those odds in your favor. That plays out in-game via checkpoint-based revival and the ability to choose a difficulty level (other than "devastating," of course).
The Arcade modification appears to be a free update to Dead Nation, but we won't be sure until PlayStation Network updates later today and the content goes live. The "Road of Devastation" content, however, costs $3.99.