On Sunday, March 30, 2014 11:30:14 AM UTC-5, Jeff Liebermann wrote:
Besides being more efficient,
upright is also more comfortable.


Really? Maybe this is true for very short rides of a few miles and minutes.. But for long rides of tens or hundreds of miles and many hours, upright is extremely uncomfortable. Being bent over on a diamond frame with some of the weight supported by the arms/hands reduces the weight borne by the rump. Greatly improving comfort.