I think the best way of describing the difference between Valued and Unvalued functions would be "Pleasant" vs. "Unpleasant". The Super-Ego is unpleasant because it is painful, while the Id is unpleasant because it is boring. The Ego is pleasant because it makes you feel strong and competent; the Super-Id is pleasant because it fulfills your inner desires. These things are "valued" and "unvalued" because we like pleasure, and dislike pain/boredom.
However, unless you're weak and can't endure a little pain and boredom, there is no reason to "hate" or "scorn" your unvalued functions.
@Pinocchio: The point of the article by Rick was to counter your claim that you can't "work on" your Super-Ego:
"Working on your Super-Ego" is actually one of the more central elements of the personal growth aspect of socionics. The Super-Ego is a major source of psychological pain, so becoming more competent in those areas will help reduce the amount of pain one feels (for example, by learning more "scripts" for the Role function).
From personal experience, working retail has strengthened my ability to handle strangers and people I don't know that well, i.e., people I'm not close enough to to be able to determine their Fi opinions of me. I've developed certain "scripts" for dealing with people in a polite and friendly manner, to avoiding making Fi mistakes. I "worked on" my Role Function and consequently reduced the amount of pain I have to endure when interacting with the outside world.
I agree with all of this. Very well put -- profound, even! I like it when somebody puts into words things I had previously felt, but not been able to express.