Nol offsets income\profits directly. So essentially tax savings all the way till its gets used. Only difference might be state(s) sourced revenues. Some will only allow certain % of income to be reduced by the NOL. They might also have different NOL carryforward/expiration dates.
$15 million in NOL's will directly offset $15 million in future profits. With an effective federal tax rate of 35% it will provide $5.25 million in direct tax savings.