Using your Xbox smartphone app to send messages, adding friends and similar tasks is usually more convenient than doing it with a controller but other than that, the Xbox app doesn't serve much purpose. There are no extra bells and whistles to the Xbox app, that has stayed the same for a long time. Fortunately, however, this is about to change.
Windows Central reports that Microsoft is currently building a new Xbox app from the ground up that will be more similar to the recently leaked pictures of the new Xbox Store as well as the Project xCloud app. It will be more modern, streamlined and also have features removed to focus on the most used things.
The same source claims it is early in development, but at least it is coming. Are you using the Xbox app yourself, and what would you like to see Microsoft improve with it first and foremost?