I just fired it up to see and it's still kind of there. For example when loading a project, there's a popup progress bar and the UI kind of janks around while it's loading. If you click anything in the UI while that's happening like a menu, the event is lost.

OK - it's loading so that's not unexpected. However my previous experience was that the same thing would happen to the UI at all sorts of surprising moments when other processes were ongoing, such as linting or using the debugger. Kind of hard to reproduce without a large project at hand though.

Then I had to stop testing and SIGKILL it because the whole application got into an infinite loop of NPEs in the UI event loop of all places!

I too experienced using intelliJ for many years and this seems largely in line with what I remember.