Looks great! Are we supposed to copy the js etc from the demo page or is your extension zipped up somewhere?
You want it done when !!!!
I have previously developed a flash-based uploader that was working reliably in Firefox/Linux. My code is open source and I'm willing to help adapt it to work with your ext.ux.uploadform extension....
My code is at http://code.google.com/p/developerfriendly/