Yes, I think it's really the FF v. non-FF issue and not the male v. female issue. I personally have been upgraded when traveling with good friends who never get to fly F and given them the upgrade as a treat since I get to experience it all the time - not a big deal for me to give it up and I think it's rude not to (even though it's not my SO I'm traveling with which is a whole different story).
Also, I don't really buy the argument re: size (i.e. men are bigger and need the bigger seat). Personally I am very petite but I have back problems so who can really say that I don't deserve the larger seat over a taller/wider man if that is how you determine it? If you need an F seat that badly due to comfort (or largeness issues) then you will buy it with $ or miles as I often do...
Of course, if you go by my "hotness" factor then I should always get the upgrade over any man I travel with.... A JOKE for the benefit of some of you
