Piwik is now available on the Windows Web App Gallery, joining the ranks of WordPress, Acquia Drupal, Moodle, Joomla, and phpBB! IIS users can install these (and dozens of other web apps) using Web Platform Installer (aka Web PI or WPI) or WebMatrix. Our thanks to the IIS, Web Platform and Tools team at Microsoft for their feedback and recommendations.
The Piwik team will continue to build and support official releases for the Web App Gallery.
Note: due to the submission/verification/approval process, there will be some delay between a release on piwik.org and its appearance on the Web App Gallery.