I too have had some scheduling problems with Delta. We have been choosing Delta over Southwest lately since we can pick our seats. The problem is that whenever they make a schedule change (and they do this a min of very 3 months-according to rep I spoke to last time) your seat assignments disappear, or even worse, they choose they for you and everytime they ahve they've put is at the rear of the plane. This can be a major problem when we connect (in ATL) and need to hurry to make our connection. Even if the flight changes by only 1 min. or by flight number, your seat choices will disappear. They are supposed to notify you by email but they aren't very good at it so I usually find out on my own by regularly checking my itinerary.
My other beef with Delta is on their credit vouchers. I bought a tix for my Dniece to come home from SLC for Thanksgiving. 3 days after I bought the tix, the fare dropped $100 (on a $250 tix) I called to get the lower fare and even after they took $50 away for the reticketing, there remained a balance of $48. They were mailing out a voucher (to my niece, since the tix is in her name reagardless of who paid for it) and as of today's date, I haven't recieved the voucher. I spoke to a rep in India about a month ago and she said she was going to send me an email, immeadiately, with ticket number to be used for credit. No email either. I've sent an email to Delta, no response. My biggest concern is that the voucher will only be good for a year and 2 months have already gone by. She could have used the credit for her flight home for xmas too!