Add Description text for image fields

There used to be a "description" field to go with uploaded images using the ImageField CCK module. This particular field made the ImageField module very useful as clients often provide copy to accompany multiple uploaded images within a single node. In Drupal 7, however, this "description" field is missing.

I have tried commenting the following line in the image.field.inc file in the function image_field_instance_settings_form($field, $instance):

// Remove the description option.
unset($form['description_field']);

Surprisingly, this seemed to work. However, I am concerned about the long-term ramifications of this solution, particularly when I apply updates to Drupal. I am wondering why this vital functionality was removed in the first place and what official workarounds there are for its absence.