This is the development snapshot of ACL for Drupal 6.
See the change log for the changes since the latest recommended release.
Note: The devel_node_access (DNA) module, which is part of the Devel module, provides an in-depth view into the inner workings of node access, especially if you enable its debug mode at admin/settings/devel#edit-devel-node-access-debug-mode and its second block. This is a big help for understanding the forces that control access to any given node.
Note the Drupal core issues listed on the ACL front page, which are outside the scope of ACL. Help resolve these issues to make ACL perform even better!