Even though I hated to see the L-fare upgrades taken away, I agree that the higher paying passengers should be allowed more benefits; however, I disagree on not allowing L class ticketed passengers to use their available upgrades after all revenue passengers are checked in.
Also, I too believe that Delta did not give FF members ample time to use up their earned upgrades. Back when Delta issued paper upgrade certificates, each one was valid for one year. Therefor, I believe that Delta, after announcing that L class fares could no longer be upgraded, should have allowed FF members a full year to use any unused segment upgrade from L class fares. If you remember a few years ago when all of the major airlines changed their FF programs, a lawsuit was filed against the major airlines. The lawsuit was successful in forcing the airlines to allow FF members the option of using earned mileage points, before the FF changes, at the old redemption level. I believe this situation is similar in that we earned upgrades based on the assumption we could use them on L class fares for 1-year from the date of the certificate.