Not a revolution
The media and Sony fan boys would have you believe this is revolutionary and about to replace books. Hardly.
It's nothing new, just it's got Sony's name on it and people go "Oooo!".
Standard limitations with ebook devices...
Small screen makes it difficult for those with poor eye sight. Yes you can increase the text size, but that means lots of scrolling around.
Small screen means it's useless if you want to replace those big reference manuals. I mean, can you imagine a Haynes on a device like this? Would you be happy having your ebook reader sat on top of the car engine whilst you read, and get oil all over it?
No colour - again with the reference manual issue in the case of those that need colour diagrams. The media has been spouting on about how students can replace their text books, but they often have these kinds of books which are not suited to a small screen greyscale ebook reader.
Annotation - yet again reference / text books. Students often like to scribble in the book to make notes. Can you do that with these? Ideally you need a stylus at least.
Cost. Needs to be cheap. Very cheap. £50 or less I'd say, else it's never going to even remotely stand a chance of replacing books.
Cost again ... attracts thieves. Imaging little Jonny walking home from school getting beat up for it. Hardly going to happen with a £5 book.
The media have also been banging on about environmental impact of books but fail to mention how Sony's factories will likely be located in China, use a lot of oil based plastics in construction, pump out a lot of pollution, and then the products will be shipped by air around the world. Compared to books which are often printed within the country of sale and paper sourced locally and these days from sustainable forests, the plantation of which encourages wildlife and often provide green spaces for recreation.
Lock-in. Whilst we can shove on "free" text files and pdfs (the latter I assume has more advanced content stripped out for simple display), Sony likely will be trying to push online stores like iTunes but for books, with DRM and copy controls, and high prices.
The "Airport novel" factor. You go to an airport and pick up a cheap trashy novel you can flick through and stuff in a bag without concern about damage. Are you going to have your fancy ebook reader with you to do the same and just want a book to read? Likely you'll have forgotten it anyway and then how are you going to download a book when you've run out of books to read? It's also another gadget in the travel bag to add to the laptop, PDA, DVD player, mobile, camera. Plus adapters, chargers, etc.
I'm sure it's fine for what it does, but people are making out it's the end of books. Hardly.
Besides. Books smell nice, and look good in book cases too :-)