For me, it very much depends on who the person asking is. I have a few close family/friends who can pick up pretty well on if I'm feeling well or not, and they don't ask me how I'm feeling, they just know, and will occassionally offer supportive comments along those lines, and similarly, if its pretty clear I'm having a good day, will offer reinforcing comments. Those are very welcome. I appreciate that they aren't a daily status check, and that they come at either high or low points on the "how I'm feeling" curve.
Comments from people I know less well, but who know I have CF... I don't really care for those at all, and just give a "I'm fine thanks"... with the implied "you don't really care, and I don't need you to care, so leave me alone."
Comments from people who don't know I have CF, but clearly hear me coughing, etc., I tend to like giving the "yeah... I have CF" with the implied "and you're an a$$".
However, I love it when its from other cyclists... for example, yesterday during a hard 40 mile ride, the group stopped briefly, and a new rider to the group commented "you left your lung back there." This gives me a chance to educate a person about CF, and, forgive me, show off... the "yeah I have CF" with the implied, "and I kicked your a$$ on that last climb, which makes me awesome..." Generally people in this situation want to learn more about CF, which if I'm in a good mood, I'm more than happy to share.
Chris
27 m w/CF