Although Autofac is not really part of Orchard's public API, it does come in handy when you need to customize how some of your classes are created and managed by Autofac.
When first starting out developing applications with Orchard, I remember well the need for more extensive documentation and samples on the API and concepts that exist in Orchard.I remember how glad I was to find Piotr's blog about the most important extensibility points. Although it didn't provide in-depth details, at least it pointed me to what services there were available, which helped me enormously getting up to speed. I kind of envy these guys who seemed to "get" Orchard as of day 1. It took me a whole lot longer before I gained creative freedom to build anything I needed with Orchard.
For a new project I'm working on, I needed to override the title that is displayed in the Content Items overview in the dashboard. This overview lists all content items, and by default, displays either the name of the content type, or, if you attached a TitlePart to your content type, the title of that TitlePart: