I scored a Kindle for Christmas, and have been busy catching up on a bunch of reading that I have neglected. Most of it is sci-fi stuff so far, but I'm also planning on ganking stuff from Project Gutenberg (as in "printing press", not "Police Academy") and some other interesting/educational texts.
The big hassle is that the Kindle's PDF reader is kind of limited. Specifically, it can't resize fonts at all, which makes reading some of the books I've got rather difficult. I've snagged Mobikit's Creator Publisher version and managed to convert both The US Army Ranger Handbook and all 24 of the NEETS modules into kindle format. Conversion seems to do great for text, but messes up formatting of stuff like tables and the placement of artwork.
Pretty slick stuff so far. Amazon did a good job of integrating their store with it and making it easy to acquire content.