Are you people all oblivious to the fact that you can find hundreds of thousands of books on file sharing networks?
I don't want this to become a debate about intellectual property rights, but let's assume for a moment that many people don't care much for that (and if digital music is any indication, that's a safe hypothesis to make), then Bob's original list of pbook advantages becomes irrelevant:
*) There no DRM on books you download off bittorrent.
*) There's a huge selection - not as big as Amazon's maybe, but definitely bigger than your average town bookstore. I've yet to look for a book that I couldn't find.
*) The pricing is of course impossible to beat
I bought my Sony Reader only after I discovered what's available online for free, and would probably never have bought it otherwise.