Used to work so well on (the old) United, they were able to gauge it and still get flights out on time. Upgraded passengers waited at the gate podium to be called and got on accordingly. Then CO's way came in (same as DL by boarding pax and then calling them back up to the front if upgraded). What a cluster - you send someone back to row 32 and then go retrieve him while he pulls and drags his stuff upstream against the tide of passengers still getting on/ settled ? If anything would delay a flight it is that scenario. Never made any sense to me, still doesn't.