Hiring a CoffeeScript.js developer brings a unique blend of readability and efficiency to your project. CoffeeScript simplifies JavaScript, making it easier to read and write. This improves productivity and reduces the chance of errors. The developer can write cleaner, more reliable code, enhancing your application’s performance. They can utilize CoffeeScript's advanced features, such as array comprehension, destructuring assignment, and classes, which can streamline your project and make it more maintainable. Moreover, CoffeeScript's compatibility with JavaScript ensures seamless integration with existing JS libraries. Thus, a CoffeeScript.js developer can deliver a high-performing, robust application.