I'm honestly just baffled by the continuing posts to the effect of Amex certificates being hard to use to a degree that is even in the same ballpark as using upgrade certificates, clearing complimentary upgrades, or finding high-value SkyMiles redemptions.

K space is halfway up the inventory chart, and D space effectively even more so (differentials to H). More than other carriers, DL's segment-marrying logic seems capricious and excessively punitive, but if even FTers think that "scoring" any discount fare is worth tracking, maybe I have more insight into why DL is the most profitable of the US majors...

I use my Reserve cert for nonstop West Coast travel from MSP, and for the sake of data have never considered it particularly difficult to do, including the Sunday after Thanksgiving. In general, I do find connecting flights to have much tighter inventory, but thankfully even with the laughable service from MSP there is still a decent schedule to major cities like SFO and SAN (as well as hubs).