I notice you have a gazillion issues asking how to enable plupload on file fields in Drupal 7. :) It took me ages to find my way to the FileField Sources Plupload module for my own need. You might consider just adding a note to the project page under the "Drupal 7 version" heading indicating that such a module is available and necessary to get that functionality. (I realize there's already a link to the module on the project page, but it's in a list with a bunch of other modules, most without explanation of what they do, and I suspect a lot of other people, like myself, would be helped by a more explicit connection.) Thanks for the module. Cheers!