The first Call of Duty: World at War map pack has been purchased and downloaded over 1 million times on for the Xbox 360 and PSN in its first week of availability. It took the CoD4 map pack nine days to do this, althought it was not released simultaneously across both consoles.
The maps are still not available on the PC.
There is no word on the split across the Xbox 360 and PlayStation 3, but Microsoft reports that it is their fastest selling piece of paid DLC to date. I'm guessing, based on this information, that most of the downloads were for the Xbox 360 version, but this makes sense as there are more copies of the Xbox 360 in the wild.
Did you get "Map Pack 1"? What do you think of the new levels?