The site seems very fast, so good job. Without being able to see a non-obscured application.js, the javascript gurus here can't be of much help. The cloudfront is doing a good job with the caching, but you could shave off 10 HTTP requests by doing a sprite of the background images (just like you did with sprite.png, although the download.gif could be moved in there too.)

I love seeing developers raise their hand on HN and say "I did this!" And kudos to you the project so far!