I've been flying DL to STT for years for annual vacation... yes a standard 757, usually the standard domestic 24F version with overhead video. Service is generally good and the FAs cheerier than domestic routes, as well as the passengers.

Normal upgrade with miles is YBM to there since it is not quite treated as domestic, but with SWU you can upgrade on K+ fare. Also found that if you want to use miles, the price of the M is only ~200 less than the I fare.

If you're not flying in peak season (winter) then I'd say ust buy lowest coach fare and you'll clear on the medallion upgrade. If you're flying during any peak or holiday time then the F cabin does tend to fill up due to mileage redemptions.