Quote Originally Posted by Bad JuJu
Interesting! I've never heard this before--bikes being built up differently for riding hilly roads or riding flat roads. But I'm no expert, so just because I've never heard it doesn't mean it isn't true.

Maybe someone else, who knows something about this difference, can chime in. Anybody?
One of the obvious things would be gearing; lower gearing to make hill climbing easier. It's been pointed out to me that changing out a cassette is pretty easy meaning you could have one with lower gearing for hills and another with higher gearing for flats and speed. From what I can see it's an easy, 5 minute task to do the switch (see link) I know some of the girls here have done it.

A second possibility is that you probably wouldn't want a bike with a longer wheel base; those are mostly designed for comfort on the flats.