It's not a UINavigationController replacement. It's a slide menu like facebook, just uses nav controller as inspiration, to make creating slide menus, that are all the rage, easier to setup use and dictate what goes on your navigation list. I will work on a better screen shot, but there isn't much for a screen shot to show. It also uses iOS containment as well.
There's no motivation here to why I, as an iOS developer, would want to use this over UINavigationController. What makes it better? What problem does it solve? The one screenshot it has looks terrible.
There's also <a href="https://github.com/pkluz/ZUUIRevealController" rel="nofollow">https://github.com/pkluz/ZUUIRevealController</a>
which implements iOS5 containment, and i think they ported it over to ios4