I am the anomaly. I choose middle row for 90% of flights. However, I'm petite, fly short runs with no checked luggage, and always carry a Travelpro Walkabout Lite rolling tote. It fits perfectly under almost every Delta middle seat in front of me. If I sit aisle or window, I can't always count on it fitting under the seat. I usually sit forward in the cabin, and many times luck up by reserving the middle seat. Since it seems many people shy away from booking an almost full row (on the 3 side), if the flight is not full, one of the seats will be empty and my row partner and I have that extra seat room.