I have some friends who are adepts of Wing Chun Kuen. Wing Chun's "Sticking Hands" (Chi Sau) operates on very similar principles to Push Hands. At the higher levels, this technique is extended to include sensitivity and sticking with the legs (as a Southern art, Wing Chun has had to develop techniques of controlling the opponent's legs to prevent dangerous attacks to the lower targets -- knees, ankles, hips, etc. -- which are prime in many of the more aggressive Southern styles).
Without exaggerating or changing the principles of Taijiquan, it should be noted that much of the footwork in Chen style is not merely stepping, but is included as part of the defensive repertoire.
I have been working on these two principles with my students, and have found that much of the footwork in both the classical forms and the modern (Wushu) standard forms of Yang style has a direct application in attacking and/or controlling the opponent's legs. This is supported in the section on Stepping in Kuo Lien-Ying's "Tai Chi Boxing Chronicle."
If anyone is interested, I will gladly share my observations.
Steve.