There was an airplane problem in Seoul apparently, and they had swapped planes for my flight to Atlanta. Turns out this plane is the first in a new fleet of long range Boeing 777-200LR aircraft to be used by Delta. From talking to the crew, it will be used at first on flights that are even longer the Seoul-Atlanta, say flights to Sydney or Dubai. The cool feature of this plane is new lay-flat seats/beds in the business class cabin.
They were very nice as a bed. I slept for more than 8 hours with no problems. As a seat, I think they need to go back to the drawing board however. I felt like I was sitting too high and too far forward. There were lots of neat shelves, controls, etc., but I felt like I had to reach back to get to them. Anyway, I enjoyed it while I could - this plane won't be regularly flying the Seoul routes anytime soon.