User experience is one of the most vital metrics to estimate the ease of use of any application. It not only adds value to the business but lets other important stakeholders project the growth of the business. User experience is directly related to the interface of the application often referred to as User Interface or UI.
One very raw and intuitive way to judge the quality of UI of any application is to find how much does a user needs to interact with UI to accomplish the desired task. The lesser the interaction the better the UI and hence richer user experience.