I can chime in here...a little. I never really thought of going out of my way to u/g servicemen (women). This was until about 2 1/2 years ago. I was flying MSP-PHL. (NW) Guy behind me called the F/A and requested to give up his seat to a uniformed serviceman. The elite was gathering his stuff, as the serviceman came forward and thanked the guy over and over.
Overheard the serviceman say to the guy sitting next to him that he had a MIDDLE seat in the rear of the plane. That was about all.
Upon landing at PHL, it was requested via announcement that we all wait in our seats until the serviceman could deplane. I was right behind him, and when I turned the corner to the jetbridge, I saw the request. A herse was waiting at the bottom of the stairs, and they were off-loading a casket with full honor colors. I waited at the end of the jetbridge for an associate, and would say a good 1/2 of the people off the plane were shedding tears. The ceremony that took place was watched by most of the people on the plane from the window.
That evening, I picked up the stack of newspapers on my porch, and read in it how a person close to my town had been killed in Iraq, and he was to be laid to rest later the next day. Not sure if that was him, but it was touching!
From that point on...ANY time I see a uniformed servicemember, I ALWAYS give my F seat up. (usually purchased F) Traveling through ATL alot, I have seen MANY young, brave souls just returning, or heading overseas!