Just got off the phone with DL trying to book DC to SIN First Class using miles this coming January. Before calling DL, I tried both AA and UA.

Within 10 minutes, the AA agent confirmed me in F on Cathay Pacific for the exact days I needed. Routing: DCA-JFK-HKG-SIN-HKG-JFK-DCA. She also offered JAL as an option (similar routing, but through NRT). Total cost, 130,000 miles.

It took longer with UA, maybe 20 minutes, but the agent came up with a really exotic routing (also on the exact days requested): IAD-LHR in UA F; LHR-BKK in Thai F; BKK-SIN in SQ F; SIN-FRA in SQ F; and FRA-IAD in Lufthansa F. Total cost, 120,000 miles.

On to Delta! After almost 30 minutes, the agent offered I could leave a day earlier than desired (ok with that), would fly DL Y from DCA-CVG; DL C from CVG-LAX; SQ F from LAX-SIN. Could only come home day after desired date and the only thing available was Y on SQ SIN-SFO, then F on DL SFO-ATL-DCA. The next available seat out of SIN in F was not for 12 days. Total cost, 140,000.

So, in addition to DL's restrictive upgrade policies, lack of comfortable Y seating, now they can't even compete in terms of honoring award requests. The only regret here about leaving DL is all the unusable miles in my account. A real incentive to earn even more miles with them, I think not!