I signed myself out of the program. Yes, it works well, briefly, if you participate in the promotional segment. That is, if you give it away. Got quite a boost from the free downloads, went to the top ten lists for my category in the US and the UK, and had a small upswing in sales after the promotion--when the book still appeared on the top one hundred lists. Then...nothing. As far as the Amazon prime "lending" portion of the KDP offer--I've had a grand total of one download.

In short, KDP is good for Amazon as it keeps ebooks exclusive to that site. But in the long run, it does nothing for the author. My term with KDP ends January 31. I'm adding my ebook again to B&N Nook books and leaving it on Amazon as is, sans KDP.