Personally, I think it has more to do with what you get used to as a cyclist. Having spend 13 years cycling long distances in Manitoba, one of the flattest and windiest places on earth, I don't like going up hills ... and I don't like going down hills. Going down is often worse than going up! Its a tremendous amount of effort and agonising pain for very little benefit. Plus I'm off and walking half the time anyway ... thinking to myself that it would be easier to have just hiked the whole thing and saved myself the trouble of pushing a bicycle.

But put me in wind, and I'm fine. I can settle in and be quite comfortable.

However, I will say that if you're heading into a hilly area, the lighter you can make your bicycle the better. I'm often thinking of jettisoning my panniers when I'm slogging up some hill somewhere.