[fjtorres]

The reports I have seen from Indie Authors--Konrath, Howey, and others--is that they see it as both a promo tool and a revenue source, a distinct and separate market, much like magazines. It pays less that discrete sales, like magazines, but it raises visibility. Other promo tools ike Bookbub cost money.
Other authors see it as an alternative to permafree.
One author reported he had a short story he had planned to permafree to promote his series but decided to put it into KU. He got decent payout and a boost on the sales side.
Just anecdotal reports but they dovetail with the consumer side stories.