On the contrary, the Coursera courses that I've taken have been nothing less than top notch. The teachers have been great and easy to understand, the programming assignments challenging and relevant, and the whole experience felt polished and well done. I did try one Udacity course, but quit because I felt it wasn't challenging and poorly done. I don't think it's fair to compare Khan Academy and Coursera, since they are teaching far different conent (algebra vs. undergraduate level courses)

Ing