I have such mixed feelings on this. I would love to see the 787 for the long, thin routes it might open up.
However, as a most-of-the-time Y traveler for work, I'm thankful that these haven't seen the light of day in the DL flights which means for TATL/TPAC I'm on mostly A330s and 767s (and the odd 77L) -- all of which sport much friendlier Y configuration and specs vs. the 787.
I feel bad for the UA flyers who will be looking at 78J TATL flights coming up soon which means an increase in 3-3-3 seating to Europe (in addition to the 3-4-3 they already face on many 777s).