I'll bite as well.
Things I'll miss:
-The red tail. There may be a lot of red on Delta's tail, but it's just not the same.
-Upgrade rates as a low level elite.
-Published mileage charts
-The Continental partnership
-The KLM J/V that was so seamless that as a young adult I thought they were one airline.
-MEM
-What could have become with the 787's
Things I like:
-Power and IFE (though, with time NW probably would have refurbished with power, I imagine...)
-The livery
-Reduction in 50 seat regionals
-Y+
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