DICE has confirmed that Battlefield 3's Armored Kill DLC is currently in the process of being rolled out on Xbox 360 and PC.

The add-on pack is in the middle of a staggered rollout, having debuted for PS3 Battlefield Premium members last week. Xbox 360 and PC Premium members receive access today, while the DLC will go on general sale later this month.
Armored Kill is all about vehicular warfare. It features four new maps, six fresh vehicles with 20 unlocks, as well as a new Tank Superiority game mode.

Yesterday DICE detailed a number of upcoming Armored Kill fixes, which are planned to go live "late this week or early next week for all platforms".