Here is a excellent demographic chart which compares the complete pricing and basic features of different eBook Readers like the Apple iPad, Amazon Kindle, Sony Reader, JooJoo & Nook.
This table of information is also useful for people who are looking to buy these readers or mini computers because it compares the most important features of all these. While for Gadget Geeks The Apple iPad and The JooJoo looks more promising because of the color display and touch screen while for the eBook Readers e Ink based devices are more useful because they are good for their eyes and also offer higher battery life.
It seems like this ignores other devices like the Adam Tablet & Infibeam Pi