The back button working even with the zooms to the next level is KEY for your audience. Well done.

Funny, as you posted that, I was adding my "excessive js animation" addendum.

It shows up as a blank page for me, with Firebug noting a Javascript error. Seems to work fine in Safari. It wouldn't hurt to make your site be able and degrade smoothly. At least show me a message that something happened, right now it just looks like you don't exist. Having it able to degrade would also let you get search engine traffic.

Indeed. Unless it has some user-agent detection for Googlebot and other search spiders, it's completely immune to search engine spiders.

I think it'd be a worthwhile experiment to add an HTML version (like Gmail) just to see the results. It should be easy enough to retain the design without all the excessive javascript.

And I'm sure a super-simple version would take much less time to develop than the current pure-js approach.

Yeah that only happens when you have FireBug -- need to fix that one