One of the more frustrating things about recurring tasks is that the values inputted for custom fields copy over to the new task. While I could see a use case for that, if you’re using the task for capturing values that might change, it becomes an annoyance and often leads to people forgetting to update values before the new task is updated and/or completed. Similarly, attachments often copy over as well and may not be relevant to the new task.
I’d propose an option (check box?) when marking a task to be recurring if you want custom fields to be cleared out, same for attachments.
Alternatively, it would be nice if it was possible to reference custom fields via workflow actions to wipe their values. As of right now, you can only do this with picklist fields, not text or numerical fields. This way a recurring task could trigger the custom fields to be wiped upon creation.