My Take
I found that Khan Academy didn't really have space for improvement if a student got a question wrong and marked their score because of mistakes. I have to stress that mistakes aren't a reason to mark down practice homework and make kids in my class feel bad. They don't bring fun into the learning process and don't explain topics very well for kids who are struggling. Multiple kids came to me explaining this matter and I am proud to say that I'm not using this program this year.
How I Use It
I am a teacher and was instructed to use this program for math with my 5th graders last year.