I find this line of discussion dubious. What you want to know is _not_ if he has spent hours preparing but if what he is saying is correct/the best way to explain something. He might be so gifted that everything just comes to him. Or he might be the person that might suck at math even with hours of preparation. Just because he said "I dont prepare for my lessons" (paraphrased) does not mean what he's teaching is no good. There is a reason why the videos have been watched as many times as they have.
The thing that annoys me about Karim's argument is
1. There is no constructive criticism. He does not tell Sal (or me the reader) how one can make SA better
2. He has a competing for-profit venture that is a direct conflict of interest with SA and leads me to question his motives
3. He is a self-proclaimed expert with no proof of his own expertise
4. From his rant, I don't get that there is something structurally wrong with SA videos in general as his claims make them out to be
How many of Khan's videos have you watched? I've gone through about 100+ of them, and the material has been universally excellent, and certainly met, (and in most cases exceeded) the lecture material that was presented to me at High School/Simon Fraser University.
"Quality and Usefulness of Khan Academy Material?" - you must have gone to an incredible school if you find his material lacking.
Absolutely I read the original criticism - carefully. It was (in my opinion) complete nonsense by somebody who clearly has an axe to grind.
I have seen over 100 of Khan's videos. On many occasions he was able to clearly communicate a topic that I had been gated on. Doing so in a clear, concise manner. I have colleagues at work that use Khan to help their children through Math. If Khan had existed when I was in university, it would have eliminated 90% of the tutors costs associated with things like linear algebra. So, as I read his criticism, I was asking myself, WTF - this feels like it has _nothing_ to do with the content that I've viewed, which has been _excellent_ in explaining topics that very few (if any ) of the lecturers I had in High School/University were capable of doing.
What it actually reminded me, was of Encyclopedia Britanica's FUD against Wikipedia when it was coming out. The criticism _sounds_ accurate, unless you've actually looked at the content being attacked.
My point is - you can't read the criticism, and make a judgement, until you've spent some time looking at the material to see if the criticisms are sound.
He's addressing an EXAMPLE the critics used to illustrate their actual point, and fails to completely address the bigger issue.
I thought the critics' points were completely valid, and raise pretty serious issues about the quality and usefulness of the Khan Academy material.