This article makes an argument for 75/76 degrees, which is seemingly becoming an increasingly more popular opinion. He also mentions that there are few bikes built with 75/76 degree seat post angles. It seems to me that building a bike at 75/76 degrees would be ideal in is much with the typical 4 cm or so of fore/aft seat movement this would cover 74-78 degrees. Some manufacturers such as Cervelo get around the problem with their variable seat post but other manufacturers without this option on a 78 degree seat post have painted themselves into a corner for those who prefer to ride more shallower. Interesting to note that Yaqui and Cervelo have brought out two new 75/76 seat post angle bikes.

http://www.tri-ecoach.com/art7.htm