At Quest Software (now a part of Dell), we strive to providing the SharePoint community with solutions that provide maximum performance, power and flexibility, while minimizing the direct impact on your production systems.
What does this mean from a SharePoint migration perspective? In order to migrate content, our Migration Suite for SharePoint leverages Microsoft's published and supported APIs and Web Services, eliminating the need to install agents or other software on the source and target servers.
We choose this approach because there are many disadvantages to installing agents during a SharePoint migration.
So when evaluating a third-party SharePoint migration tool, remember that it's more than just moving content from point A to point B. It's important to consider the approach each tool takes.