workflow per-state field settings: implementation preview

I've implemented the per-field settings functionality in a separate module called workflow_fields at http://drupal.org/project/workflow_fields.

The functionality should work for any CCK content type, although I haven't tested each and every field type. The usage is as follows:
* Create a workflow and associate it to a CCK content type.
* The workflow state form lists all the fields of the content type and allows each field to be set as visible/invisible and editable/read-only, for the current state.
* When editing a node of that content type, fields will be hidden or disabled depending on the state the workflow is in.

LIMITATIONS:
* The creation state is not handled: all fields are editable.
* The 'view' tab of the node is not handled: all fields are displayed regardless of the state.
Those limitations will be addressed in the near future.

Your feedback is appreciated!