I was gonna label this post with with my standard 'book reviews' but I didn't think it would be fair to do so as I had no experience with any other e-readers as a point of comparison and seeing as I only review the quality of publisher's books after I've gotten my hands on at least three of them. As of right now, I've only read one book on Kindle.
It's a sexy little piece of hardware. I'm no technology geek, but found it to be solid and well made. While the extreme light weight of the Kindle was a bit disconcerting it didn't feel flimsy in my hands and the weight felt expertly distributed throughout the entire device. The buttons have a nice solid 'crunch' to them when pressed--I enjoy that kind of feedback--and the words on the screen couldn't be easier to read. There are other hardware aspects I could mention or dwell on but it's all around well done, so I'll skip on to my reading experience.
I have to say that my feelings toward Kindle are a bit jaded as the only book I've read on it was terrible. The Silver Chair by C.S. Lewis is by far and away not the strongest entry in The Chronicles of Narnia. If Kindles were like books, I'd be trading this one in next time I visited a used book store. I mention this only because the book did color my feelings in using Kindle.
Maps, while not crucial in The Silver Chair but perhaps vital to something like The Name of the Rose, suck ass on a Kindle. It was grainy and failed to raise any of the curiosity that maps usually hold over me in reading. Maps are particularly bad when they span multiple pages as you can't see the whole thing at once. The only issue I noticed that suffered more than maps was illustrations.
The pictures in The Silver Chair by Pauline Baynes looked bad; especially so as I had the physical book on-hand to compare. While I didn't read the book for the pictures, any added bonus they may have imparted was negated by the poor quality of their rendering.
My biggest gripe with Kindle is the words on the screen. One screen's worth of text is not a 'page.' The percentages of a book's completion as displayed by Kindle really didn't work for me. I think this is no fault of the Kindle rather my long established reading history doesn't base my progress on a percentage, therefor seeing one doesn't really resonate with me. Worse than not having a good feeling as to how much I had read, was not being able to see if I wanted to read further.
When I come to a page break, chapter's end, or otherwise feeling like I'm done reading at the moment I always flip ahead a bit; looking for the next page break or chapter's end etc. If the next chunk of text comes to an end in six to eight pages, then I'll keep reading. If it's thirty more then I'll stop reading for the time as I originally intended to do. I can't do this with Kindle and it drives me crazy. As noted before one of Kindle's screens doesn't equal a page of text and I haven't spent enough time with the device to reconcile the difference.
It's a brilliant piece of hardware. I still think it's greatest promise is in educational systems: eliminating 'new editions' of text books every semester by way of a download, decreasing the weight of backpacks by an estimated 843%, and least of all dropping the cost of printing text books and the expense of already broke students having to buy them. Assuming publishers and authors can ever figure out away to make a viable business model out of e-readers I think they would be very well received as an educational tool. As for me, I could never get over the fact that I was reading a Kindle and not a book.