it's worth noting that it can't work on mobile - mobile safari does not support any kind of file uploads. But not working in IE is definitely a fatality
It's worth noting that iPhone does not equal Mobile. What about Android? Even if Chrome is the only Android browser supported, that would be plenty!
Once we get filepicker.io working on mobile browsers, sites using filepicker.io would allow users files directly from Dropbox, Facebook, etc without the iPhone directly supporting it.
And yes, we are working on IE support.
We now work on IE8+ as well as mobile safari and android