i have encountered a few people who have tried to improve seating - usually works in person more than on the phone - but by the time you have in-person contact, it's too late to get a better seat. (full)

three rows from the rear toilet on an SFO to ATL flight does not make me so happy.....

Just booked DTW-ATL-HSV yesterday through our corporate travel agents site which does not allow me to put in a NW FF # for Delta. I tried calling Delta to have my # added immediately, but apparently they were having issues with the phone system (not the normal automated voice response garbage system) and I gave up after 20 minutes. I tried changing my seats online this morning. They system let me select them, but did not honor my requests when submitted. I called again and got through right away to have my NW # added. Immediately went back online and this time it honored my exit row requests. Second time in the last 3 weeks I've done this, so having your WP# in does matter.

I've not had lots of experience with DL but over Xmas 2004, my NW number got me preferred seats and on a February trip to Budapest on DL and AF, the ST elite plus status showed up on the boarding passes and got me preferred seats on both the DL and AF flights.
I may have called and made special note of the status.
tom