Yes I would pay extra to get on a Southwest flight and I did about a month ago because I was flying cross country and I wanted to have my choice of seats since they do not have preflight seat selection. I got on the plane and grabbed the seat with the greatest leg room and I enjoyed the flight. The herd of people that followed were fighting for seats and overhead bggage space. The people who really made out getting on the plane first were the wheel chair bound and their families. It's worth the ten buck charge but I wouldn't forty.
The next question is are you willing to pay early boarding fee for cruises. I wouldn't because it's not such a big deal to get on a ship early and the way they line you up in the hall prior to boarding makes you feel like all people are equal.