I like how both the app and the screencast are a bit rough - yet he still released them without being concerned that they aren't 'perfect'. Super great start on this - I'm sure he'll get some great feedback.
In the demo, he says your keybindings are dependent on your OS. I use Linux, which is probably part of it. If you're on a Windows box, it's supposed to make it more like Windows keybindings. Presumably at some point he'll make it a preference option thing.
edit: oh duh, you mean firefox. yeah, you'd have to change your firefox bindings.