I just went thru this -- it didn't work. I checked every hour and nothing opened up that I could pick, they were protected.

Seems like it would have been an advantage to have no seat, because then I would have been allowed to pick something protected, since I can't check in without a getting a seat assignment. And if the only seats open are priority/EC, etc, I must be allowed to pick one. Somebody in coach got them without paying, and it can't be anyone who already had a seat assignment.