I haven't had any issues with NW in-flight lately -- 11 segments on NW/KL in March (mostly NW) and all was hunky dory.

Earlier in the year I did TTU a couple incidents of no-preflight-beverage service with no good excuses, but in the March flights (with one exception that I mulled over for a couple days and decided if I couldn't make up my own mind I wouldn't TTU it) everything was either up to snuff or there were obvious reasons (late plane/catering, awesome cattle call boarding that packed the aisles full). All of the FA's were great, no 'tudes on exhibit.

Maybe we were lucky, but that's our recent snapshot of NW -- all in F, of course.

DL really is a different situation. As the airlines were headed into C-11, DL made an effort to maintain & improve their in-flight service in contrast w/ the NW "race to the bottom". It's why I can stand to fly all day in Y on DL but not on NW.