Bagua practitioners are quite familiar with the name Zhao Da Yuan, and recently Tom Bisio released part one of a sit down interview with Zhao. Amongst other things Zhao discusses Bagua origins, theory, and has this to say about Taiji push hands practice:
"In Ba Gua Zhang, we do practice sticking and rolling hand exercises. Today many Ba Gua teachers incorporate practice methods into Ba Gua. I do not like this. While pushing hands practice trains sensitivity, it is not so useful for real fighting. Real fighting is fast and unpredictable. One must focus on the ability to change and transform quickly according to the circumstances and pushing hands is does not train this. Train footwork, speed and the ability to change. Speed is important in martial arts. Not only does speed help you to hit the opponent, but it also increases your power."
Click here to jump to the entire interview!
Without a doubt the most comprehensive analysis of joint manipulation from the CMA perspective is Zhao's pivotal work "Practical Chin Na" translated by Tim Cartmell. This is also the most complete info on Zhao you will find in English.