I noted the likely result that some content will end up being exclusively B&N, if their service convinces them to leave Smashwords and such... exclusivity will be a benefit to them. But really, I expect they are mainly doing it to maintain a tighter control over what gets published, and how.
As far as authors and self-publishers are concerned, the situation will likely be much the same as it is on Amazon: For those who cannot publish or sell their own work, for instance, on their own website (the way I do), the service gives them an outlet for their work. But unless you can effectively advertise yourself, most authors will see limited exposure and small sales, as they'll find it difficult to rise to the top in a digital market that is still dominated by Big Pubs.
Finally, the press release mentions output in DRM'd ePub, but does not specify if it will be mandatory for self-publishers to use DRM. Along with other details of pricing and other options, it will be interesting to see what they finally offer.