I spent some time today pondering this offer. It makes me uneasy. The exclusivity thing rubs me the wrong way, and I would never do it with a book that was selling meaningfully in other stores. Not sure if I'd do it at all, just on the principle of the thing. Though I did consider maybe enrolling a book that was selling poorly, just to see if it would help. But there's that alarm bell, very quiet in the back of my head, warning me of...what? If Amazon gets an even larger share of the market than they have now, how long before they start carving back the royalty? Or offering the best royalties only to those authors who sign up for their exclusive programs?
I like competition among the booksellers. I'm not sure I want to undermine that, even if it might mean some extra money in the short term. (Probably not that much extra money; let's be honest.)
Writer Beware offered some cautions about it:
http://accrispin.blogspot.com/.
I'll be interested to see how other writers react to it.