I was there about an hour ago. Line went pretty quickly for Shake Shake. 20 mins tops. They offered biscoffs and lemonade while you waited in line. Greeted by a pilot and other crew members (as well as many amex/delta reps). Seating turnover was quick too.

I don't remember them asking me for my card, only if I had one. No reservation list either (meaning I could probably go again tonight without problems/have a friend go with my card). No way can I eat that twice in a day though!