I'm working on a set of modules for migrating an sf-active site to Drupal 7.
These modules depend on https://drupal.org/project/migrate - an excellent framework for migrating content from other sources - as well as https://drupal.org/project/features for setting up custom content types, fields etc.
You can find it at https://drupal.org/project/sfactive and also mirrored on gitorious at https://gitorious.org/sf-active/drupal
My goal is to support migrating everything, including passwords, uploaded .txt files, calendar events, feature stories, etc. No reason to lose anything when migrating.
It is not yet usable at all, but I figured I should encourage myself to finish it by developing in public. So if anyone is interested in this, please let me know so I am motivated to dive in and finish it, and also feel free to file feature requests on the drupal.org project.
If you'd like to discuss the feature set or otherwise get involved in making this happen, please subscribe to the issue queue at https://drupal.org/project/issues/sfactive and post your comments and issues there.