Reports say the new big brother of the Kindle family sports a larger 9.7-inch screen (more than a third larger than Kindle 2), and can rotate to landscape display just by turning the device. It also can display PDF documents without converting them, and it has 3.3GB of memory (no SD slot). Also, some of the big newspapers (New York Times, Washington Post, and Boston Globe, to start) will offer a subsidy for subscribers who sign up for long term subscriptions but can't get home delviery— no clue yet on how much.
Some big textbook publishers are also putting out for Amazon— Addison-Wesley, Wiley Higher Education, Longman & Prentice Hall, among others. Amazon has gone ahead and signed up schools (Arizona State, Case Western Reserve, Princeton, Reed, and Darden School of Business at the University of Virginia) to "distribute" Kindle DXs to selected students. I didn't see any details on how that will work as far as cost to the students.
The SlashGear post includes a video demo and the press release text.