Mark Jamra, writing at TypeCulture:
There was no desire for a revolution, no attempt to create something startlingly new and unique. I was not looking to fill some vast hole in the spectrum of typographic style. After all, it was to be a basic sans-serif - how many holes are left in that area? And yet, it happened.
Look at the activity and warmth in this Expo Sans specimen. The flip side of the ‘admiring specimens’ coin is reading stories like Mark’s — the forces behind typeface designs.
See also Drawing Letters, written by yours truly after attending TypeCon 2010.