Originally Posted by
joe_miami
As I recall, my seat for the first segment was assigned automatically at T-24, which I believe is standard for anyone who uses a Delta mobile app. I got the dreaded "at gate" for the second segment, but my seat was actually assigned several hours earlier (again, notified via the app).
Is this a B2B (back-to-back) itinerary?

What you are describing has happened to me.
With regards to BE, I have had generally good luck on Delta flights. Almost on all occasions, either I have been assigned with an aisle or a window seat, or I have made the switch (when allowed/available) myself. On the rare occasion I have assigned a middle seat, and there are no aisle or window seats, I have had good luck with seatmates not showing up, seatmates getting upgraded, sometimes the entire row to myself. For short-haul flights (e.g. LGA-BOS), whether 3-3 or 2-3 configuration, I will continue to fly BE.
The frustration part is DL block open seats, even at T-24.