> That said, I have always wondered how effective video is as a teaching tool for programming? I guess when I think about it, it's the same delivery tool as an in-person lecture, but in some ways, more effective since you can pause, rewind, etc.

I've dug up a lot of papers on effectiveness of teaching strategies in physics in particular (since I'm a physics student), and it seems in physics that your time spent working practice problems and making predictions about experiments is more important than actual lectures.

An example:

http://www.sciencemag.org/content/332/6031/862.abstract

If anything, I think the Khan Academy is best suited for a mixed approach where students watch lecture videos, then attend a problem session or help session to work examples, get help on exercises, and so on. The Khan Academy's exercise framework is an important step in this direction, and I hope they continue to improve it.