As an instant-on, full-page web browser, it's far more useful than a netbook, but it's pretty underwhelming for everything else.
With shorter battery life, greater cost, and more eyestrain than the Kindle, I doubt it will have much impact on the e-reader market.
If Amazon dropped the price to sub-$100, I think they'd sell them by the boatload, but at current price points... nah.
And the majority of the general populace doesn't give two hoots about iPhone OS and App store limitations. You and I might, but I wasn't talking about technophiles - my mom has no idea that the restrictions even exist. She's just pleased as punch about how easy it is to use.
Like I said, it's a fine netbook killer (though I think the segment was killing itself). But there is no way this thing is taking market share from the e-books.
It's a bit heavier than the average book, but it's by no means a brick. This claims that it puts it at roughly the 75th percentile of books in terms of weight: http://wiki.answers.com/Q/How_much_does_1_book_weigh