The Cold Stream DLC is readily available to all PC and Mac users today, but Xbox 360's users are going to have to wait a little longer, thanks to a delay for its release.
According to the L4D Developer's Twitter, today just isn't the day for Left 4 Dead 2's DLC to release, apparently they're working on it, but who knows when it'll happen?
This delay probably isn't tremendously surprising for many who have played the level, since even in its Steam-ready version, a few bugs still exist around the seams. Ultimately, though, it may just come down to the normal processes that go in to this sort of stuff.
Regardless of when Cold Stream comes to the 360, the price has already been set: 560 Microsoft points, or $7 in human money.
Remember, though, for PC version, that price is reduced to free dollars, and it's available right now through Steam!