I made a mistake: the Kindle has always had an option to transfer files to it via USB. You are not forced to transfer files via Amazon's wireless network, as I had previously stated.

There was no mention of this on the Kindle product page in the section on "personal documents," which only discusses the email option. Because of this, I assumed email was the only transfer mechanism. Being able to use USB makes a lot more sense.

BTW, the new, large-format Kindle was announced this morning: 9.7" display, 3.3 GB of available memory, native PDF support, ~$500 USD (which is crazy expensive).