We have recently been toying with the Drupal API module in an attempt to set up our own Drupal API documentation site just like Lullabot did. As of today we have managed to set up something that is fairly functional and somewhat similar to the Drupal.org documentation site. Check out our own Drupal API reference site.
The site currently contains documentation about the top 500 Drupal modules and their D5, D6, D7 and D8 versions in addition to the documentation for Drupal 5, Drupal 6, Drupal 7 and Drupal 8.
In the process of setting this up we came across multiple limitations of the API module because it was never intended to generate documentation about so many different modules and so many different versions of each modules. We had made some quick fixes to make the site functional and get this system up on a trial basis. We also added a custom menu to list drupal projects that have been documented in the site as it was lacking in the api module.
Because this is still an experiment we have not enabled commenting on the site. Boost module has been set up on the site because the site has been pounded by bots recently because of the huge number of individual URLs in the site.