Flew DTW-AMS RT last month in PS.

Being a fat dude, the seat to me is worth it 100%. Didn't feel as spacious and cushy as F, but million miles ahead of economy.
Food was gross, but I attribute this to Delta's desire to go "cuisine". What happened to regular good ole pasta?! Plane food is never the highlight of my day, so it doesn't matter anyways.
FAs were attentive enough, no complaints. (As a side note, I'm not sure why people seem to be afraid to use the call button??).

Bottom line, just as expected, you are paying for the seat (same goes for D1).
If you can fly TATL in economy without having to visit a chiropractor (or a proctologist) afterwards, there is no reason to upgrade to any other class.