http://educationnext.org/can-khan-move-the-bell-curve-to-the-right/
This article is a pretty good description of the promise of Khan Academy but minus some of its criticisms. Maybe the last paragraph is telling: "'You can't just put a kid down in front of a computer,' Goines said, although the kids I saw in Julian's, Cadwell's, and Negash's classes sure seemed to enjoy it."