Day one. I loved the first one immensely and will buy the second in a heartbeat. Ranks as my favorite third-person action-rpg murder-simulator ever at this point.
Shadows of Mordor and DOOM will always be generation-defining moments for me with my Xbox One; much like Halo & Kingom Under Fire on Xbox classic, Twilight Princess on my Gamecube/Wii, and Just Cause 2 on 360.