I booked a flight a couple of days ago (DL 284) from LAX-ATL a few weeks out, this is domestic service but on a the 777 with 4 cabins, but all PS seats were already taken. I have FC/C+ upgrade marked on the reservation and went and set a seat alert on EF. Sure enough yesterday morning early (4 am) the alert says 2 seats avail (I just need 1). I got up an hour later and I go to the app and see nothing in the PS cabin and was thinking someone snagged the seat already. I double check my UG request status, and then went to check EF to see if the alert was still active (I'm new at this) and it was and showed the 2 seats still there! I read something here on FT regarding unchecking UG and rechecking so I decided to just try it before I called in. YEP, unchecked just the C+ ug and saved, then rechecked and saved and I was immediately moved to the open aisle seat...

Just a heads up that now that you can't even see what seats are open except the class you booked, you won't know what is there unless doing a dummy booking or using some other tool. If I didn't know about setting an alert I would not have seen the seats open up, and certainly wasn't upgraded to one. About as transparent as a brick wall.

If you're using EF anyway, you can easily see DL seat maps there and even save your searches. IME seat changes appear there almost instantly, although the automatic searches for requested alerts are run in sweeps according to a schedule.