Amazon's Kindle is now out. Amazon has done a great job at delivering a whole solution and not just a reader. Assuming that the device is ergonomically usable that you can download content from anywhere via the built in mobile phone technologies is key to its success. No docking. No bluetooth. No wifi. Just seamless ubiquity to the new and updated content.
Update: I was at Border's yesterday (2 Dec 2007) and saw the new Sony book reader. While I am generally attracted to bright and shinny objects the reader and it's display looked scuffed and forlorn in the long shallow of the Kindle.