I think that is the Seiler piece on the 2 waves of training adaptations. What he came to was intervals worked very well but at the elite levels efficiency was king. Intervals and power work obviously have their place but if one aspires to be elite in endurance efforts...you will have to log some efficiency hours. Even in this case if one uses intervals as a base and focuses the long efforts on establishing race pace and efficiency of movement, I think you have a powerful formula there. Straight from the power running site.
"Survival will be neither to the strongest of the species, nor to the most intelligent, but to those most adaptable to change."