At this time I don't have a need for a Kindle, but I can see where it might come in very handy, particularly for those who are on the road alot and don't want to carry around a bunch of books.
In my case, most of the books I read are those that I intend to keep, either for research purposes (books on films, bios, etc) or for sentimental reasons (the Benjamin Kritzer books, books by people who I know, etc.), so a Kindle would not be a good investment for me....maybe when I retire and have time to read a wider selection of books something like that might come in handy.
I think it is nice to have this option for those it would suit.