This review is for the whole Specialization, not just course 1. The lectures & subject matter are fascinating, but the course itself has some serious limitations:
1) Two of the most common example problems the instructor uses are image segmentation & speech recognition, both of which have been completely superseded thanks to neural networks (CNNs for the former, RNNs for the latter). The course was written in 2011 or 2012, and the lectures haven't been updated since.
2) The textbook is extremely useful, but they do not provide a PDF, though it is easy to find via Google. The professor does not give explicit "readings", you just have to find them on your own.
3) The Discussion Forums are effectively dead, nobody involved with the construction of the course has gone through them in 4 or 5 years, and most learner comments are several years old as well. In other words, you're on your own as far as figuring things out.
4) Quizzes & exams have no partial credit, often have "gotcha" questions, and enforce time delays between attempts (1 hour for quizzes, 24 hours for exams).
5) By far the biggest problem however is the programming assignments: they must be done in Matlab/Octave. I've taken many other courses outside this Specialization, so I say with confidence that the lion's share of the learning occurs in solving programming assignments. In the 3rd course especially, the programming assignments are exactly the same ones assigned to students taking the course in real-life at Stanford, where it was assumed that students would work together in groups to solve them. They are not of a reasonable difficulty level, from a pedagogical standpoint, for a distributed, asynchronous, online course.
All of these problems ultimately stem from the fact that this was among the first courses on Coursera (Daphne Koller is one of the founders of Coursera), before they really understood how to properly convert between a university course and an online course. Unfortunately, where Koller's colleague Andrew Ng has put in a lot of work updating his Coursera courses, Daphne appears to have abandoned this (to be fair she is very busy running companies doing fascinating work).
I recommend Andrew Ng's Deep Learning Specialization and University of Alberta's Reinforcement Learning Specialization for learning ML content, though the former can be quite hand-holdy at times.
Good luck,
Max