Kwf also provides default controllers for user management (create/modify/delete users). For basic usage add the following controllers to your Acl:

$this->add(new Kwf_Acl_Resource_MenuUrl('kwf_user_users',
        array('text'=>trlKwf('Useradministration'), 'icon'=>'user.png'),
    $this->add(new Zend_Acl_Resource('kwf_user_user'), 'kwf_user_users');
    $this->add(new Zend_Acl_Resource('kwf_user_log'), 'kwf_user_users');
    $this->add(new Zend_Acl_Resource('kwf_user_comments'), 'kwf_user_users');

The user roles a user is allowed to manage are defined through Acl roles (Kwf_Acl_Resource_EditRole), an example how to create an additional role explains this best:

 $this->addRole(new Kwf_Acl_Role('myrole', trl('My Role')));
 $this->add(new Kwf_Acl_Resource_EditRole('edit_role_myrole', 'myrole'), 'edit_role');
 $this->allow('admin', 'edit_role_myrole');

In addition you can change the behavior of the user management controllers by inheriting them any changing the Acl accordingly (to point to your custom controllers)