Update Dec 12, 2012: Thanks to the users who reported this error regarding license expiration: "The License has expired. Please download a new version of the Active Directory Replication Status tool from the Microsoft website." Please download the tool and run the installer again to fix this issue.
We want to make sure users are aware of a great UI-based tool that is available on Microsoft Download Center for monitoring Active Directory Replication. The Active Directory Replication Status Tool (ADREPLSTATUS) is a free tool that analyzes replication status for all domain controllers in the forest. It shows replication results in a UI that is customizable to help you spot and prioritize errors easily. If you miss having the old Replmon tool that has been deprecated since 2008, this is a good replacement tool for you. Thanks to Microsoft MVP Sean Deuby for writing an article about ADREPLSTATUS in Windows IT Pro magazine. We plan to publish additional articles about how to prevent Active Directory replication problems from occurring and how to use ADREPLSTATUS soon. We also have a home page on TechNet Wiki where users can submit feedback, feature requests, or share tips and tricks.
Justin [Active Directory Documentation Team]