This is the new 6.x-2.x development build of the XML sitemap module. This 6.x-2.x branch is a complete rewrite with considerations for performance, scalability, and reliability.
Upgrading from any 6.x-1.x versions is now supported, but still in testing. Before upgrading, make sure to backup your site's database. Please report feedback on the success/errors for your update.
The research, planning, and development behind this branch is done with my own free time. Donations and sponsorships of any amount are welcomed and help me keep active in contrib development. To donate, please visit http://davereid.chipin.com/. It is also recommended to read http://blog.davereid.net/content/state-of-drupal-xml-sitemap-2009 for a summary of the overall progress of the module and development.
Testing status: http://qa.drupal.org/pifr/test/26130