Having no idea what went on between Yavin IV and Hoth (I know nothing about any EU), I can't say that she was of no substantive use to the Rebellion (she proved herself a darn good shot with a blaster on the Death Star). I like that she might (also) have provided some nifty PR benefits via her patented hologram-communication style guaranteed to elicit sympathetic action.

Come to think of it, though, I have no idea whatsoever what could have possibly happened in the ranks of the retarded rebellion to have the likes of Han Solo and Lando Calrissian promoted to generals. Not lieutenants, mind you, not majors. Freaking Generals. What in the universe could have happened between ESB and RoTJ to have Han Solo promoted from captain to general?

So don't get me started on ladder-climbing within the heirarchy of the Rebel forces. It seems to make no sense whatsoever, except to appeal to prepubescent fanboys. For all I know, they kept Leia around for the pretty face alone (though I heard she begged to be taken to the planet full of white powdery stuff, and was pretty pissed off when it turned out to be snow).