Took time to find out this one. To set title or label for a fivestar form field you need to add
'#title' => t('Your rate'), to your code, so it should go like.
$pane_form['rating'] = array(
'#type' => 'fivestar',
'#default_value' => 100,
'#title' => t('Your rate'),
'#widget' => array(
'name' => 'some__stars',
),
);