I loved this course - I just happened to see it mentioned on Twitter, a few weeks before Christmas, and it made me very happy at a time when there wasn't much to be happy about.
It's a fairly easy course. There's no heavy-duty music theory; the explanations using simple diagrams are accessible to anyone, and truly enhanced my understanding of the music. Prof. Kelly is just charming, and conveys his love of music. Part of the material is also the history of the piece, and that turned out to be just as interesting as the exploration of the musical structure.
FMI see my personal blog post at https://sloopie72.wordpress.com/2015/12/03/need-a-little-christmas-handel-and-chill-messiah-mooc/