I started using the free version, but when I realized what it could do, I bought the paid version with all functionality.
Having tasks and calendar items on one screen is most useful. The three classifications of tasks was an added bit of functionality with unexpected usefulness.
I would definitely give this app a try. The help is informative, not that you will need it that much. This app is really quite intuitive.
Cyberq about Task and Cal : Easily Manage your Tasks and Calendar