I've been frequenting the Delta lounges for years at various airports. The evolution has been striking - the Delta lounges today are far nicer than the ones I visited 20 years ago. Bigger, more food/drink options (it used to little more than 'bar snacks' - now you can enjoy a well-rounded meal appropriate to the time of day). Also visited Korean, EVA, BA, and Singapore airport lounges - no major complaints although crowding was occasionally an issue. Last time through JFK, we were entitled to the Delta lounge - but there was a massive line waiting to be let in (not that it mattered - we had a short layover and even if we'd been able to walk right in, we'd only been able to stay a few minutes). But that's been the exception - not the rule.
I can also use the American Express lounge (although only when traveling on Delta) - only visited one but it was very, very nice.
My wife and I flew Delta One out of Seattle a few months ago (on our way to Indonesia) - they now have a special lounge just for Delta One (if you're not familiar with Delta - Delta One is their premium international product). Instead of the open, buffet style that's the rule at the other lounges, the Delta One lounge was more like a fancy sit-down restaurant - with special menus and food prepared to order (but no bill to pay when you left
). Unfortunately - due to a brain fart on my part (long story) - we didn't have much time and couldn't wait for a proper, prepared meal before we had to go board our flight. My wife (who absolutely loves all-you-can-eat buffets) didn't like it at all - although if we'd had more time and she could have ordered off the menu, she might have liked it better.