• Support has been added for a new PipelineVariable common parameter in the context of iterative pipelines, such as those used by System Center Orchestrator; that is, pipelines that run commands simply left-to-right, as opposed to interspersed running by using streaming.
• Parameter binding has been significantly enhanced to work outside of tab completion scenarios, such as with commands that do not exist in the current runspace.
• Support for custom container activities has been added to Windows PowerShell Workflow. If an activity parameter is of the types Activity, Activity[]—or is a generic collection of activities—and the user has supplied a script block as an argument, then Windows PowerShell Workflow converts the script block to XAML, as with normal Windows PowerShell script-to-workflow compilation.
• After a crash, Windows PowerShell Workflow automatically reconnects to managed nodes.
• You can now throttle Foreach -Parallel activity statements by using the ThrottleLimit property.
• The ErrorAction common parameter has a new valid value, Suspend, that is exclusively for workflows.
• A workflow endpoint now automatically closes if there are no active sessions, no in-progress jobs, and no pending jobs. This feature conserves resources on the computer that is acting as the workflow server, when the automatic closure conditions have been met.

Source: http://technet.microsoft.com/library/hh857339.aspx#BKMK_workflow