But just for the sake of argument here is my take:
I would gladly pay $800 for a device that can download magazine subscriptions, books, watch movies, surf the internet, write emails, etc. Sure your iPhone and Macbook Air can do these things to. But can they do what is showed in this link?:
http://gizmodo.com/5428619/mag%2B-c...lishers-shows-thinking-outside-the-tablet-box
The markets for all these devices overlap to a certain extent, as do the functionalities. But who cares? Many people carry phones around that have MP3 capabilities and still carry an iPod. I would buy this thing, since it would most likely be lighter than my MBP, and I have some money to spend.
Many people here seem to think that this thing should introduce a whole new way of computing and address a totally new market. I don't think this is true. This is basically an evolution of what is already there. If you don't like the thing than don't buy it. Don't expect it to cure cancer and respond to you waving in front of the screen. Expect a touchscreen device without a keyboard, dedicated apps, some new reader functionality ad increased portability and I think you won't be disappointed.