The other downside to these free (just about always) and discounted (sometimes) ISBNs is that they link the publisher as the service you got the ISBN through, rather than yourself, even if you're doing what would classically be considered a self-publishing job. How big of an issue is that? IANAExpert, but it seems like there are some nooks and crannies of IP law that can be swayed by owning the imprint, but little practical concern for the average person putting an ebook on Amazon e.g. Perhaps someone with more in depth publishing knowledge can color the risks better than I.