Interesting idea, I don't expect to be lined up outside Staples at midnight on launch day
Battery life and outside reading are pretty much the only advantages of the kindle over the fire for me. I guess this feature would not help much on a sunny day and will likely adversely impact the battery life.
As I read more (I read a lot of technical boooks), I am finding the kindle screen a little small for displaying images with words. I end up having to change the orientation to closely examine charts and images. The Fire is a little better in this respect due to the screen size and a LOT better due to the ease of reorientation.
I do, however, see how this could be the only reader for many people.