I have a Sony Ereader (Kindle wasn't available in the UK when I bought it - and I was not too impressed with the idea that you can't download kindle books on to a pc and they can zap them at will!)
I can read the designed for purpose ebooks, PDF files (all those 'free report' downloads!) - and - I haven't tried it - but MS Word files as well. Here's a link you may find useful:
What is a Reader? : Sony
You can even put photos on it (though they render in grayscale not colour) and listen to .mp3 files on it.
It can take additional memory cards - eg I'm using microSD in mine in an adaptor.
You can't wirelessly download which you can with kindle apparently, but I don't see that as much of a problem compared to the benefits of having backup storage on computer and being able to read a variety of formats sourced from anywhere.