I found the lectures entertaining and the exercises of a much lower quality. Not enough of them, shallow and ambiguously worded.
I got something like 90% on the edx MITx probability course and was barely getting 50% for the above mentioned Stanford stat learning course for the 5 weeks of it I completed. I mention the MIT course, (which I highly recommend fwiw) only to support my view that I don't think my experience is aptitude or workload related. But as ever YMMV.
[1]: https://lagunita.stanford.edu/courses/HumanitiesSciences/Sta...