I'm also interested in the use cases for Planning. We were very interested in using Planning, especially for the Goals part to have a general overview of all our goals and the execution of projects/programs within those goals. We just thought that Planning was not yet sufficiently developed. However, I was impressed by the looks in Planning, e.g., the Gantt Chart in Workfront looks less visual than the same view in Planning. In the end, we decided not to use it for now.
For the future, I hope that Adobe will keep on developing Workfront for non-marketing companies as well. At the moment, all we see in communications is almost only marketing-related.