Scientific study on the effects of good font use
A Recipe for Motivation: Easy to Read, Easy to Do: Scientific American
Of course, they used two horrible fonts. Their good font: Arial is really very poor. It is just good when compared to Brush. What if they had used Amitale, which is designed for readability or even that old standard Garamond or Caslon, or Bembo, or even Baskerville?
Imagine what would have happened if they not only used readable fonts, but a layout designed for readability?
This stuff is really important.