I have been a delta sky miles member for many years. In the past year or so, I have witnessed very poor service - they cancelled flights, delayed flights for maintenance problems, which has negatively affected my vacations. The last trip I took, they caused me to lose 2 out of 5 vacation days.
Worse than this is when I call customer service, they are rude and uncooperative. In Delta's case, the customer is always wrong and the problems the customer encounters are never the responsibility of Delta.
I advise passengers to rethink their relationship with Delta Airlines and go elsewhere to meet your travel needs.