Given I have only AS status, I flew Delta recently when AS wouldn't get me there (which is basically anywhere east of the country, or east going east).
I find it amazing Delta has such a hodgepodge of airplanes and yet seems to still have them decent (maintained well). Isn't it supposed to be when planes are standardized things are much easier? Like all Boeing?
I find their pilots are very visible (on the few flights they are either in the galley as you exit, saying goodbye, or standing at the door of the cockpit). That is an important bit, as it is basically your last memory of the flight, and can turn a neutral experience into a positive (with a face to attach to the flight).
Their flight attendants don't seem as grumpy, and do seem more caring.
And I also trust them more in terms of actually getting you there, even with a connection.
So I flew Delta from MIA, which is no easy feat (given it is AA's hub).