Black Ops 3's Nuk3town map is going free for all players. Previously, the fan favourite was confined to a pre-order bonus, and, for UK boxed copies, a Game-exclusive pre-order bonus at that. Given that Game's PC selection is unlikely to tempt a Steam user, I can't image it was busy on PC.
There was some confusion as to when the patch (1.08) drops—Activision announced that it was live on all platforms, Steam users said otherwise—but now Treyarch's director of development is indicating we should expect it later today.
