Not the OP but my impression with asyncio was that it's great for the uses case it was built for (hence the "no problems") but if you need to do something a bit different it can become an annoyance (hence the "unexpected bugs").

I see it for a specialized solution for a specific class of problems, which can lead to surprises if your problem evolves. There are always trade-offs to be made (performance, flexibility, hardware cost, etc.), asyncio just has different characteristics than the alternatives. Maybe since a upper bound of concurrent users it is always a great (the best?) solution, someone with more experience along all the design and requirements space could comment.

First for the syntax it is quite not good, you have to use await and async keywords plus async everything version of all that you are using.

You can't mix non async code with async. And you can easily do in some way and block your application without you noticing.

And in the end, async is not even really async, just cooperative execution.

I'm a big fan of Python since very low version. And I don't have too much difficulty using async/asyncio now I'm used to it, but in all honesty I don't think that it is really great in the grand scheme of things.

He's probably one of the people who didn't bother to read the documentation.