Jscodeshift is remarkably easy to write scripts for. It is why I'm very comfortable using all kinds of experimental babel plugins: If somehow the proposed standard changes or just never makes it and I want the code to be es6 compliant (or, say, move it over to a different compiler), then I know that for most cases I can easily write a codemod that makes the changes in our codebase.

Nice examples are stuff like decorators or the :: bind operator.