I've been on Khan Academy for over 3 years now, and this site has saved my ass more than once. Just last year I was struggling with calculus before a big exam that might have seen me out of university early, but I watched these videos on Khan Academy and did the exercises and I passed (after maybe a week of thorough practice).
Now I'm doing linear algebra and I'm struggling hard. I've attempted to watch the videos on this site, and even though they are more advanced than most stuff around here, I still grasp the concepts roughly. My issue is that there simply aren't any practice exercises on linear algebra. Moreover, the videos go so fast from concept to concept that I'm having a very difficult time solidifying any of the information given, not to mention there is a serious lack of content over there.
Another reason why I'm writing this is because if you look at all the content on this site and its quality, linear algebra just doesn't hold up very well compared to, say, statistics or calculus.
Therefore I beg of you Khan Academy, please, please add some practice exercises to linear algebra and maybe check out some of the comments on the more frustrating videos. Please.