I bought one for my wife, it came yesterday, I'm impressed. Very easy on the eyes to read a long time without eye strain. I find the not-bright white less strain on the eyes.
I've been buying technical literature as much as I can lately as PDF files. Partly because they are cheaper and I was not liking the pile of books in boxes in the garage that are now obsolete, taking up space and I don't know what to do with them.
Beyond being able to send MS Word, HTML, TXT and images there are converters for PDF and other ebook formats that once converted will make them available over your wireless network. True the formatting of these methods tends to get munged but are quite readable.
Last night I bought an Oreilly PDF about Facelets, sent it to the email address of the Kindle and within minutes was comfortably reading.
As for the tiresome rants about DRM from the basement dwelling, mouth breathing geeks that know nothing about a Kindle...
Re-read the above, read more about what this thing can do, look at one, note my sig
And get off my lawn!