I have mixed feelings about the Khan Academy, or at least some of the reactions to it. It is being hyped by some as the answer to our failing school system (a premise I have doubts about to begin with).
It seems to me that it is more or less a simplified textbook in video form, made available for free. Now this is not a totally insignificant thing: free textbooks are nice, and some learners will surely learn better from watching videos than from reading a book. It does seem to leave out some pretty important aspects of learning such as motivation and teaching the reasons and ideas behind why we solve math (and other) problems the way we do. It also seems to be, other than its medium, pretty much the opposite of innovative, in terms of educational theory.
Nonetheless, for an adult independent learner who wants to brush up on some long-forgotten high-school math…someone a bit like me, for example…I can see it being pretty useful. So I’m giving some of its lessons a try.