I was looking for something like since the day I installed Joomla. I wanted to have a sidebar with various additional links and info that suppliments the article. Like list of anchors, and various others, that are specific to each article.
I tried mod_custom, but that's a pain, because I need to have a module for each article that I want to supplement. Awkward. With this extension I can keep all relevant info with the article, making it much easier to administer.