What I got from the Khan Academy TED talk (TedxNJ video not out yet) is that he wants to change education by giving students just in time learning.
Do you want to know how to solve this type of problem, cool here’s the video. You will remember it because you choose to watch the video when you realized that you have to know how to do stuff for homework. It is better than the teacher lecture because students only watch when they think, “Shiznit I need to know how to do this to do my homework”.
With the teacher directed lecture the student sits through the lecture is bored and tunes out. When homework comes around s/he says, “Dagnabitt I should have paid attention during class”.
They still tune in and out of the Khan video, but they have the option of going back to the step they missed and re-learning it.
Khan works better than teacher lecture because students watch the video just before doing the homework, then they watch bits and pieces of it over and over again while doing homework until they get it right. (if they care enough about doing homework).
I’ve seen teachers do this on a regular basis in schools for year. They lecture for half the class period then give students the rest of the time to do homework. Students are to raise their hands if they have questions? This actually, works better than the Khan video (when the students aren’t busy talking about relationships instead of doing homework) because the teacher can explain in an alternate way.
In the end the result is the same, students learn math by practicing procedures over and over again until it sticks in their memory.
What would I do different? Well I would probably show the video after the lesson as a summary or something, but that isn't the important part. The important thing is how would you use the videos?