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.
"Quality and Usefulness of Khan Academy Material?" - you must have gone to an incredible school if you find his material lacking.