I think that what most of them are missing are testing hard questions and projects without hand-holding. Many of the courses I have taken have been good, but th

I think that what most of them are missing are testing hard questions and projects without hand-holding. Many of the courses I have taken have been good, but they will just graze the surface of anything approaching harder mathematical questions on tests and projects are too "fill in the blank (function)" rather than requiring critical thinking. I took one Udacity class and I certainly felt like I had been cheated, more cutesy animations and polished videos than real content. I would use them for an introduction, but would definitely pick up a well recommended textbook after, or do a medium sized personal project after. Although the Coursera Cryptography class I took was just as good as my University one so I guess it really depends.