I'm not a Kindle user. In part, because it's not available in the UK, but also because it seems too closed in terms of its overall architecture. But it's clearly winning fans - and I think that's going to be a problem.
Why that might be is revealed by this interesting
posting:
Reading .DOC and (some) .PDF files. This part of the Kindle's function turns out to be much more important than I anticipated.
Mine can't be the only line of work that involves an endless stream of material to read, often arriving as Word .DOC or Adobe .PDF files. I resist printing them out, and I resent the additional hours of sitting in front a computer screen to read them.