I have tried to use Khan for years and it is still not teacher friendly.  For example, if I assign several things, for example the complete set of videos and articles for completing the square, which has 11 parts. I want to extend the deadline for all 11 pieces, I have to click on each of the 11 and manually extend the deadline for 3 different classes. If I want to extend the dead for one student, well, now I get to do it all again. I tried deleting assignments for another students to modify it, but when I unchecked his name when editing the assignment, it just freezes.  

Also, if I want to give students points for the entire clump for completing the square, I have to click the next button and look at two different pages.  There is not reason the only 7 assignments appear on the screen.  Oh, I know I can download the .csv file, but that even harder to read.  So, no, I still don't like it as a teacher, still.  But I try, every year.  Every year it gets a little better, but still not seamless.