In the late 90's I was flying from FRA-ATL in J that had been upgraded from Y using a PMU. I had coordinated schedules with a friend of mine to be on the same flight. He had a full J ticket. We were both surprised when they upgraded us both (a double upgrade for me) to F.

I remember the vodka and caviar, and getting an extra tin to take with me. Since it was a daylight flight, I didn't care that much about sleeping so I didn't test that capability of the seats. The PTVs back then just showed several channels of movies in rotation (no on-demand) but the screens in F were much larger. The service was, of course, great.

While it is a shame that DL doesn't offer international F anymore, it was hard to justify it economically. No business would buy a F seat for employee travel and the price difference for F made it hard to justify even for the high-rollers. And of course, they aren't making any money on the upgraders and award pax.