The situation of employees going on vacation or medical leave has come up often in Answers and everyone has been trying to figure out the best way to deal with this type of scenario so that current Forms tasks can be reassigned to specific users as well as new tasks.
Our organization uses a SQL table that is used as a data source and determines the various approvers in different areas of our processes, so assigning new tasks isn't a big issue for us.
However, the ability to reassign currently assigned tasks in a more automated way is something that comes up regularly. One idea I have is a Workflow activity that is able to search for all tasks assigned to a specific user in a specific process and then reassign them to a specific user. This would allow for greater automation of the reassigning of tasks while including all of the functionality that Workflow provides, such as database queries, custom Workflow activities, scripting, etc.
One example of using this functionality could be a form created for users to request vacation or leave. After approval it could update a database table with the dates the user will be out. A workflow could be scheduled to run the beginning of each day against the table. For those out for the current day it could see if they have tasks assigned to them and if so, reassign all Forms tasks to a static user, or a user submitted as part of the form. Other databases could be queried as well.