For our apps that support the Agenda/Calendar view  you can you can filter out completed tasks by tapping the filter button on the top right corner and unchecking the “Include Closed Items”.

If you are in the Tasks list view you can filter out completed Tasks by setting the filter located on the upper left hand side next to the Grouping button to “Open Only”.

You can also hide completed items (including tasks) from the Hot List by going to the Settings –> My Settings view, scrolling to the “Hide Completed Hot List Items” section and setting the value of Hide to Yes.  (This setting will soon be moved to the Hot List view itself.)