This video is the recording of Ash's presentation at FITC Screens 2012: http://fitc.ca/presentation/500px-for-ipad-a-developers-behind-the-scenes/
The recording was unfortunately cut short due to camera problems, but covers about half the content.
The 500px iPad app first shipped in October 2011. Since then, it's seen extraordinary success in the App Store and has been featured by Apple as an example of what visually stunning apps should be. Ash Furrow presents the story of building a native photo application with a focus on user experience, responsiveness, and immersion. He discusses the technical challenges, pitfalls, and redemptions of building the app for the World's Best Photography.