One function that isn't available in most planning apps is long-term tracking of projects or major tasks. It would be extremely useful if when I created a task, I had the option to 'check up' on the task over multiple time periods, such as daily/weekly/monthly. This is different from simply repeating the task each day/week/month because you should be able to change the title of each of the multiple reminders, and you can do that while editing a single task/project.
