I'll give you two examples, one from a consumer viewpoint and the other as someone working in the travel industry.

This year, I traveled on Thanksgiving Day, not a time when most people want to be working. The FA I had on that flight was just fantastic - she smiled the entire flight and it felt genuine, not a fake-smile-plastered-on-her-face look. She provided excellent customer service on a day when I'm sure she'd have been much happier being home with her loved ones.

From a travel industry perspective, I book air for 100+ plus groups a year and Delta's group department is the best. I deal with groups from all over the country and have to deal with every airline and while DL does not always have the air I need at the fare I need, the group department staff are a pleasure to work with. If DL services the route I need, they are always my first call.