Kindles can read a variety of non-proprietary, non-DRM'ed formats. They read TXT, HTML, JPEG, and non-DRM Mobi files directly.
If you read some of the Kindle discussion groups, you'll see people complaining about "no backlighting", and then a few days/weeks later they will be lauding the fact that it has no backlighting.
There are converters available from Amazon and/or Mobi for pdf and doc files.
Granted the PDF converter seems to have some trouble with graphics PDF's, but for books the converter works very well.
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