The Kindle is already able to read more than just Amazon DRMed content, it can handle a number of formats.
Hack let you convert encrypted Mobipocket files that were intended for another reader so that that work on Kindle.
Ebook readers have extremely high contrast/readability and are extremely energy-efficient, being able to display several thousand pages of material without needing to recharge. eBooks are a narrow product, but they have their own ways in which PMPs cannot compete.
Plenty of free e-books in Mobipocket format show up fine on Kindle.
A revolutionary portable reader that wirelessly downloads books, newspapers, magazines and blogs to a crisp, high-resolution electronic paper display that looks and reads like real paper, even in bright sunlight.