Again, not a premium product measured internationally, but IMHO the best on the US market (and LAC where I fly regularly for work).

I complain as others do but their service is dependable and standardized (in a positive fashion). Also, DL has always come through for me in situations where there were partner flight cancellations with complicated reroutings via Twitter, and in helping me get "emergency" flights due to personal emergencies on a moment's notice.

So, when I am flying in the Americas, if I can I opt for DL.