This module interfaces with the awesome uc_file modules (File Downloads in core) to allow users who have previously purchased a File Download product to access new additions.
In other words, Product A has downloads attached to it - when an admin adds another downloadable file to the product, they can choose to add the new file to the Queue. When the Queued file is Processed, a list of all users and order numbers that contain this product is shown as each user (the owner of the product) is granted access to the new file. So now, everyone who has already purchased Product A now has access to the brand new file.
This is working in a live production environment, and tested fairly heavily. If you have any feature requests let me know. There are a few TODO's in the module, which is pretty well commented. I'll be working on these and updating the module accordingly as each new feature is completed.
Drupal 6.x version is out!
I committed a Drupal 6 version of the module to d.o.: http://drupal.org/project/uc_file_retro
While it says it's still in "dev" the module is fairly well tested on file download features that are specific to a certain SKU. Testing is welcome
The module is now fully hosted on drupal.org: http://drupal.org/project/uc_file_retro