The fastai courses do teach a lot of good things, but “good Python coding” without a lot of qualifications probably isn’t one of them.
Jeremy has been very outspoken that he doesn’t like Python and the fastai library clearly shows. There also are a lot of clever hacks around writing terse code that, shall we say, might not be universally seen as writing clear code for a library that can be built on. Now I do have a washlist of things I think are not so nice in PyTorch (e.g. spectral norm via hooks, default initialization, nondeterministic kernels…), but the structure of the API has been given quite a bit of thought and it shows.
The fast ai library versions 0.7, 1 and 2 seem to be really completely separate things with little bridges between them. The more mature PyTorch bits have been very stable since 0.4 or so (but if your code still uses 0.1.2/0.2/0.3-style Variable(..) a lot there is something to do…).
Don’t get me wrong, there are a lot of nice things to be found there and it is worth looking at, but – at least if you believe there is some truth to the Zen of Python –  there are also lots of things that are really dubious fads in terms of how things are done.
As for the lectures, they are great when they do show how to get results with neural nets, but in my opinion they are weaker when they go into “how to design a library”. For this reason, I would recommend Part II 2018 over the 2019 version. (Starting with the outright bizarre “Python is 1000 times too slow” claim in the first lecture 2019 that has been qualified in the second to last lecture when it didn’t support the story anyways, but never made the errata list of the first lecture.) So lots of great insights and a refreshing style, but the frequency of dubious claims seems a bit higher than, say, what you get with e.g. the courses Stanford put online.
So if the university-style lectures you can find are not to your taste, fastai’s offering is one of the very cool ones out there and one that doesn’t dumb down things wile being very accessible. That is quite some achievement.
I should really write a more in-depth review, but the above was my impression of the main pros and cons.
Best regards
Thomas