Halo 3 ODST will have 2 disks in the box (no matter which edition it is or if you pre-ordered or not). The first disk will contain the Halo 3 ODST campaign and the new firefight mode (think of a Halo version of Gears of War horde mode) that you can play online or offline. The second disk will contain all of the Halo 3 map packs that have already been released and the new half of the mythic map pack. It is assumed that this disk will have all of the features that were in Halo 3, except for the campaign. This should mean that matchmaking, forge, custom games, and theater mode will be included on this disk. You should also be able to play with people using the original Halo 3 disks, just not on the new 3 mythic maps till these get released on Xbox Live for download normally. We shall have to wait and see if these things are really true, but hopefully they are.