This looks like an awesome idea. I haven't been able to try it out yet because I'm running FF 3.07 (simply because Ubuntu repos haven't brought it up to 3.1 yet, and I don't really want to bother that much atm), but it reminds me of the controls built into some FPS's and even old Lucasarts Adventure games like Full Throttle or Grim Fandango. Except the default actions in this case are all favorite websites. Nice to see Mozilla labs pushing the envelope yet again.