It's been three weeks into the programs. I find them all very useful. some are more than others.
The AI class is the least approachable one, at least for me. Till date, I still haven't seen how to apply the knowledge in real life. The content is pretty dry an less practical. Most of the time, the two instructors taught us about mathematical concepts such as probability, Bayes rule, and lengthy calculations instead of some usable examples. I hope few units more into the course, we'll see more concrete examples. Besides, this may be only me again, I can't find slides for review purposes! Must I watch through all the videos again? Besides, I occasionally failed to catch the words, both visually and acoustically.
On the other hand, the DB class is very understandable in general. It does throw in difficult challenges, and sometimes utterly complicated ones, to pique the brain. These challenges are good yet quite frustrating or even demotivating. Take for example Relational Algebra quiz. Things that could be done so easily in SQL such as MAX function are undoubtedly hard in RA alone. Then again, I'm not an excellent student, so this may be only me. I only wish Prof Widow would speak a little bit more slowly.
The ML class is in between. It is approachable and practical. I can follow Prof Ng quite easily for he speaks slowly. I also find the quiz okay, at an appropriate difficulty for me. And, best of all, I can use Octave to try out what he teaches right away. You have to agree that is much more hands-on.
Overall, I highly applaud this initiative of the professors to bring world-class courses to the masses.