It's great that you're contrasting Khan to ALEKS. I'm not drinking the Khan kool-aid; my kid just started using ALEKS in the last month and I agree it's terrific. It's really puzzled me why Khan is getting all this attention when ALEKS has been around so much longer (and seems to be better in many respects -- just lacking instructional video). It would actually be terrific to have some kind of integration between ALEKS and Khan -- to be able to see a video lecture on a particular topic would be quite useful for the student.