I took it when it was on edX and found it much more accessible than the first edition of the book (which I started and never finished when I found the video course).
It's presented by Gregor Kiczales, who gives a compelling introduction here that explains the rationale behind HtDP, and is what lead me to take the course: https://youtu.be/dJbpHukiQ7I (it's fine to start from ~2 minutes onwards).
I still find myself using the process he outlines (defining the purpose of functions up front, describing the data they work on, and giving examples before writing code). I'd describe it as a sort of, “extreme inline readme-driven development[1]”.
If anyone did this course and has since read the second edition of HtDP, I'd love to know what more it adds.
[1]: http://tom.preston-werner.com/2010/08/23/readme-driven-devel...