Brick if you get R2 I'd play through single player first or else the 8 player Co-op might be confusing, if you'd like to do some MP between single player I'd love to try that out and finally get some use out of my headset.
Apparently it's an expansion of the single player. I think I'm on the last stretch of the single player.
I'm very impressed with the boss fights and some of the levels feel well epic. Defiently Insomniac did a better job this time around with the game. Something Bungie should take note of as I thought the Halo sequels where pretty lackluster in the campaign mode.
I'm still going to hold off on Far Cry 2 if I get it, it'll be on PC most likely or I might, might try it on the 360.