I think they look good in pictures (don't really like the middle one though, I guess I like the plain nude/black look better) but I'm not sure how I would pull it off. I think you would have to dress very carefully so it doesn't come off too sexy. But I have been knitting these link and thinking of ways to wear them out (maybe with ankle boots) so maybe I'll try that!
I think you absolutely have to be well coordinated, and don't wear knee highs that are too thick. Get some with the consistency of tights or leggings. I like the pictures but I don't think I have the balls to do it myself.