1. Considering it has actual paid developers working on it for quite a while and VC funding, it still lacks a great many features that I took for granted in all the non-commercial TUI libraries, e.g. menus and dialog boxes.
2. The async nature of the library is unpleasant. Can never be sure when/where your code will run.
3. Lots of 'magic' Python variables and methods that you have to override, but there's no way to discover them in your IDE through the type system.
4. Using CSS for laying out a TUI app makes no sense (unless you are a web developer and have Stockholm syndrome from using it for web apps?)
5. It seems to leak memory.
Eventually re-wrote the app from scratch using a different library that gets far less hype and spends no time marketing itself. The result was much better in every way.