Although the site looks very swish I think it's problem is that it relies too much on client-side scripting. You obviously have PHP server-side scripting at your disposal so in my humble honest opinion I would be inclined to use PHP's built-in file sever system to upload and catch all the necessary information about the file that you need and report back to the user via a self-submitting POST form. I see you also use AJAX so this would help with not having to reload the page everytime the user made a selection change.
Relying on the server-side scripting would eliminate any reliance on any browser dependancies and allow for multi-browser, multi-platform compatibility. By all means use Javascript to help validate forms client-side for ease of use but do not rely on it as many users disable Javascript (at least for unknown sites) and I would not allow ANY website into my Trusted list due to Internet Explorers inherent flaw that it is far too integrated into the operating system for my to be happy at granting a web-based application free access (hence I don't use IE
)
Of course, this is just my opinion and please don't let this deter you from a potentially brilliant business venture.
