Coursera

Anyone heard of or used Coursera? It's a website that offers courses from many of the top universities. You get a certificate, not course credit hours. Just wondering if anyone had used it and what your opinion of it was. Here's a blog about it from TED: http://blog.ted.com/2012/07/18/completely-free-online-classes-coursera-org-now-offering-courses-from-14-top-colleges/ and here's the website link to Coursera: https://www.coursera.org/