The article posits the question, "What type of e-reader is easiest on the eyes: the black-and-white screens that simulate ink on a printed page or the back-lit color screens used by computers and the iPad?" The answer is "it depends." This is worth a read if you are shopping for an e-reader.
There are other considerations when choosing an e-book reader including physical characteristics of the device (size and weight) and the ability to easily understand and use the controls to 'turn' pages and the amount and type of books available on the e-reader.