A couple of weeks ago, we bough a reconditioned Kindle from Amazon Warehouse Deals. Basically, if someone buys something and sends it straight back, then the warehouse checks it over, and certifies it for release. I find this particularly pleasing, not only because it cost £70 less than the brand new alternative, but also because it fulfils the key environmental principals of reduce, reuse, recycle.
As I'm still working my way though my Christmas books at the moment, I've only read one book on the kindle so far, but I've been very impressed with the usability, readability of the e-ink display, and also the fact that I have a number of books open and it knows where I am in each book.
The other key advantages are that books are searchable, and that you can highlights sections that interest you. I now find myself wanting to highlight sections in the paper backs I'm reading!