It's difficult to pinpoint just one most valuable feature, as there are many features that can be beneficial. For the specific use case of my client's project management office, they found the project management features of the application to be particularly valuable, such as project boards, reporting, and the ability to customize views. Additionally, task management and project scheduling were also highly utilized. However, capacity planning was not used as much as the others, as there was a lack of support from executives to invest in training and implementing it due to a lack of processes in place. The project planning features, dashboard, and reporting capabilities were considered the most valuable.
