http://www.joystiq.com/2011/10/09/update-bound-for-the-binding-of-isaac-demo-available-on-newgrou/
New final chapter, new character, over 20 new items, 3 new bosses, and more achievements.
And I was already pretty damn satisfied with my purchase!
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Falcon Punch
http://www.youtube.com/watch?v=FFtw7qW7Vcw