Jilang, yes I have watched most of these lectures, although I have never actually watched any of them all the way through. I still find them to be very helpful to a point. What inevitably happens though, is that I will start out with a very good grasp of what Prof. Susskind is talking about. I will understand it perfectly. But then he begins to use terminology with which I am unfamiliar. At first I can deduce what many of the terms are, and what they are referring to, and I can disregard others, but eventually I get to the point where I really have no idea what he's talking about. He's using terms that I don't understand based on earlier terms that I didn't understand. Until I finally get to the point where I go, I can't follow this anymore, I'm lost. I'm getting bits and pieces, but for the most part he's lost me.
It's not the concepts that are confusing me, it's the terminology. I'm sure that if I could ask him to clarify certain things, and he had the patience to explain them, that I would find the vast majority of what he teaches to be perfectly simple and understandable. The parts that I do get, I understand and agree with. Still I watch them every now and again, and hopefully I understand a little bit more each time. One of these days I may even get all the way through one of them.