If you're good enough and steely enough to make it through all six stories in Resident Evil 6, you'll be able to run through the bonus Ada Wong campaign. In terms of value, RE6 is presenting a pretty interesting proposition with the fresh approach to campaigns and the Agent Hunt component where you'll be attacking other players in their games. This isn't as awesome as being a Tom Cruise in Mission Impossible zombie, like I initially hoped, but Agent Hunt sounds pretty cool nonetheless.
If you make your single player experience available to Agent Hunt mode, other players will actually be playing as zombies in your game trying to attack your Leon Kennedy or whomever you're using. The best part is you, as the player, won't be able to tell which zombies are CPU-controlled and which are human controlled at a glance. Agent Hunt mode works in two-player co-op or single player with AI partners. Also, two "hunters" can join into an Agent Hunt mission and keep respawning as different zombies every time they die. So in the ultimate scenario you'd have two agents running through a level and two zombie "hunters" chasing them down in a meta game of cat-and-mouse. This should work swimmingly and turn the survival horror genre on it's ear...if it hasn't been chewed off already.