Here is an interesting note -
"It's surprisingly easy to get non-Amazon material on it. I just plug it in to the USB cable which perpetually hangs off the back of my laptop, and it shows up as a hard drive. I drop .txt and .mobi files into the "Book" folder and they show up. I convert a handful of PDFs to .mobi files using Mobi Creator and they work perfect, Tables of Contents and all. Sweet."
http://www.gamerswithjobs.com/node/36063