The result of the deal is two-fold. First, it increases Amazon.com's competition with Apple iTunes. Second, the music will be sold without digital rights management software, or DRM, nailing another coffin in an on-line music distribution model based on limiting user's experience with the media.
...and again, this is good for the consumer! More choice, more options, more freedom. It now seems inevitable that iTunes will need to lift its DRM software in order to offer consumers a competitive product.