My killer feature is when you want to streamline your workflow. Adding a new test runner on VSCode for your favourite language? Possible but takes a lot of effort to get right. Adding one in emacs? I can inspect the source code or my language bindings and add/change the command it’s running. In a few dozen lines of elisp I can add shortcuts to all my daily tasks and even combine them. Search for an error message I get in my tests on Honeybadger? Check. Run code snippets in org mode against my local machine and export the whole document as PDF or markdown to our wiki? Saves me a few minutes here and there