They have put a lot of emphasis on making the actual reading experience very book-like, and use the "electronic paper" technology which was also used in Sony's e-book, which I haven't experienced (yet) but which has good reviews. And the form factor is quite book-like. But then they've added in additional technology where it makes sense, like having a built in dictionary, bookmark capabilities, etc. And of course you have all of the good features of shopping at Amazon like book reviews and recommendations, and it is automatically tied to your existing Amazon account.
I'm always interested in significant new innovations in how users interact with technology (like the iPhone), and this seems to me to be a candidate for something in that league - in fact it could be more significant than the iPhone if successful, in terms of changing the way people do things (reading, in this case). So anyway, I was sufficiently intrigued that I have ordered one to give it a try - it should arrive tomorrow, and I'll report back on my experience.