I took one course to see how they work (you can take them them all for free):
I actually tried to take more courses but I found the course delivery method to be exceedingly boring. Every presentation had the same setup a talking head speaking monotonously.
In addition the material that is presented is very plain and simplistic. Overly simplistic for that matter. There is a lot more to bioinformatics than just how to type this or that.
The lecturer provided so little context and so few explanations that went beyond the very basic that I was perpetually asking myself - why not just provide this information on a website or in a book? In what way is this better than a book that would contain the same information?
I think that is really what the MOOCs have not yet figured out, how to use videos and online presence to augment the learning process rather than replacing a book with something else.