CNN has an article on the age old frequent flyer dilemma of "who gets the upgrade" for couples. Basically there is the simple view: "The person that earned it gets it" and everything else.
So would you give up an upgrade for your spouse/partner? For me I offer it to my wife first, decline it second, take it third but require her to take it next time I get one offered. In that order I would be offering to decline it unless my wife supports my accepting it, essentially she gets to nix it if desired. That's just me, I think it is important that an upgrade not be an issue and it just ain't that big a deal for me.
My buddy who flies a lot more has done the "swap" during a flight but has also had that option disallowed by the crew (when that happens they just switch to "the next flight" the other gets the upgrade).
So what about you?