As of CRM 4.0 the sitemap and isv.config file are no longer available on the file system but stored in the database. Which means that for each change you have to export the customization, make your changes and then reimport the customizations file.
This tools is indented to make this easier.
With this tool you can simply connect to a server and click a button to open the ISV.config or Site Map file. Now you can edit the file and just click save to send it back to the server.
To avoid errors in the xml file a schema validation option has been included. Validation can be run seppartly but is also run automatically when you save the document.
Version 1.0.2 includes an option to open the file in Visual Studio and benefit from intellisense, syntax validation and highlighting. Changes made in visual studio are automatically tracked on save and optionally also automatically saved to crm.