This isn't that big a deal for me. We long ago ran out of room for books, most books I buy I give away. I only keep a few, and those I could continue to buy as paper books.
Most of my books are ephemera. I'd need a house for books alone if I kept them all.
The bigger objection, for me, is that the Kindle can't read PDFs or any other eBook format:
Daring Fireball: DUMI agree with DF. More than the DRM, it's the closure to any other format that marks this as a gift horse in need of dental inspection.
...With iPods, while the iTunes Store is the only source for DRM-protected content that iPods support, you can easily fill your iPod with any popular non-DRM audio format other than WMA. Kindle supports a few other formats than its proprietary .azw, but the only way to use it for its main purpose — as a digital reader for popular mainstream books — is via its own proprietary DRM-protected format. I.e., Kindle actually is what ignorant critics have claimed regarding the iPod: a device designed to lock you in to a single provider of both hardware and digital content. You can easily and happily use an iPod without ever buying anything from the iTunes Store; without Amazon’s DRM-protected content, a Kindle is the world’s worst handheld computer...
Update 11/19/07: DF might have been unfair. It's true they don't do PDF (a big negative), but Kindle can accept .DOC, txt and a few other formats.
On the other hand, you can't use it during takeoff and landing, or when you're stranded on the runway. It's electronic, remember? This alone would rule out the Kindle as a travel companion. Back to the paperback.