Currently the filename and content attributes of an upload widget are lost unless the upload button is set to submit. It would be helpful (and surely very easy) to store that information regardless of what you're doing after the upload within that screen.
Currently if you want to do an ajax submit you have to store the information in variables if you need to use it elsewhere within that screen. Plus there is no warning or explanation of why the attributes are blank when using an ajax submit and that can be very confusing if you don't know.