FAPI Should Honour $form_state['storage'] During Form Building

I'd like to see FAPI honour the $form_state['storage'] structure during form building. That is, before the form has been sent to the user for the first time, the form builder callback is called with a $form_state structure, which contains a 'storage' key; if the builder stores things in the 'storage' area, this information should be maintained throughout the life of the form.

For a discussion of this (and some 6.x bugs), see http://drupal.org/node/158746