It's an addition, but I also see it as a temporary stop gap until the real color digital reader products become viable. I'm not sure why it needs "defending." It is reasonably enough priced and there will always be some tech-heads who want to buy new stuff. It'll do okay. There's no shame in owning one.
Some people who just can't wait for whatever reason might buy it now. But many will simply wait for the superior technology and most who do will probably be in the market for the superior technology in a year or so.
I seriously doubt even Barnes and Noble expects this to be a long-term cornerstone of their business. They'll quit selling it for something better sometime in the not so distant future.