What have you used it for? From Anarcat's notes, it sounds like it isn't very generally applicable.

It's great for running unit tests on save, or hacking on python script and re-execute them when you need.

I often use something like this when iterating over stuff. This is a quick hack to list files I touched and differ from main.

    git diff main --name-only --relative | entr -r -c my-command

This of course needs to be killed and re-run if you want to pick up new files

That's a great tip!

It's great, but I switched to watchexec for its easier CLI. (But mac users, watch out for https://github.com/watchexec/watchexec/issues/864, hopefully fixed soon.)