Hiring a Grand Central Dispatch (GCD) developer is beneficial for efficient, concurrent programming on iOS and macOS platforms. GCD developers are experienced in managing and optimizing tasks for the best use of system resources, improving your application's performance and responsiveness. They leverage GCD's advanced queueing system to execute multiple tasks simultaneously, avoiding common multithreading issues, like race conditions and deadlocks. By hiring a GCD developer, you can ensure a smoother, faster user experience, increasing customer satisfaction and potentially boosting your app's ratings and popularity.