I could afford a biz class ticket, either to Europe or Asia. My company will pay for it, but I find that paying a lower Y/B/M fare and using SWU/PMU or miles saves A LOT of money. If I didn't pay attention to the value of the ticket, I'd be on SQ to asia, and AMS, or Virgin to London. Heck, why not move my business to UA and upgrade the Biz tix to F.

Those who find DL's route system convenient will fly them for that reason. But given a choice, I'd pay for the best service, and DL has a way to go to be on par with most foreign carriers.