The app provides you with access to your Firefox browsing history, your bookmarks, as well as recently opened tabs. Furthermore, it lets you use the Awesome Bar without Firefox; simply start typing and find your most often used websites just like you do on the desktop version of Firefox.
It's a very interesting app for heavy Firefox users. Personally, I'm lost without my Firefox bookmarks, and this app would let me carry them around wherever I go; the fact that the actual webpages are rendered in Safari is not that important to me. Of course, it's still not as good as having a full version of Firefox, which could (for example) also sync your passwords, but it's definitely the next best thing.
The application is coming to the iPhone soon; for now, you can check out a video preview below.