AWS Machine Learning University is one of those resources that I am slightly surprised is not talked about more, because the underlying proposition is genuinely strong, which is that Amazon took the internal curriculum it built to train its own engineers and scientists in machine learning and made a large chunk of it freely available to the public. When a company that runs machine learning at Amazon's scale decides to give away its training materials, that is worth paying attention to, and the quality broadly justifies the pedigree. My favourite part, and the piece I most often point people toward, is the set of accompanying video lectures, many of which are on YouTube, because the instructors have a real knack for the visual, intuition first style of explanation that makes genuinely tricky ideas click, and on several topics I found their explanations clearer than far more famous paid courses. The breadth is also respectable, spanning tabular machine learning, decision trees, computer vision, and natural language processing, so it is not a one trick offering.
Where a prospective learner needs to keep their eyes open is on two fronts. The first is neutrality, because this is Amazon's curriculum and it is quite naturally framed around the AWS way of doing things, with examples and tooling that lean toward the AWS ecosystem, and that is not a criticism so much as a fact to price in, since you are getting a view of machine learning from a particular and commercially interested vantage point rather than a vendor neutral academic one. The second is structure, because MLU feels more like a well stocked shelf of high quality individual courses and lectures than a single hand held path from zero to competent, and you are largely responsible for sequencing your own journey, deciding what to take and in what order, without the guardrails, deadlines, and community that a paid platform provides. It also quietly assumes a degree of existing comfort with Python and the underlying maths in places, so I would not hand it to a complete beginner and expect a smooth ride.
Weighing all of that, my honest assessment is very positive within its lane. As a free supplement, and especially as a source of clear conceptual video lectures to sit alongside a more structured primary course, AWS Machine Learning University is excellent and costs you nothing, and the only thing I would caution against is treating it as your sole, linear curriculum or forgetting that its perspective is shaped by the company that produced it.