I got a Kindle for Christmas this year. I've only had the thing for a week, and I'm already convinced that it's one of the best things ever. I probably wouldn't have ever gotten around to buying one for myself (I tend to be really indecisive about buying new technology because I'm always afraid that as soon as I do the next generation will be released), but now that I've got it I love it.
Probably the fact that I do a lot of reading on the subway makes me love the thing the most because even with the case it's small and lightweight - about the size of a thin trade paperback, it's easy to turn the page with one hand (even with gloves on), and it will lay flat on a table without being held open so it's easy to read while you eat in a restaurant or coffee shop. No longer do I have to only read paperbacks on the train because hardback books take up too much room in the bag. I also don't have to worry about being out and not having anything to read because I've finished my book.
There's a fair amount of free content if you want to read older classics, but I do suspect that I will end up spending more on books now, in much the same way that I started spending more on music when I could buy albums on iTunes with one click and didn't have to go to the store to get a physical CD. The Kindle seems like the perfect solution for reading books that I don't mind paying for but don't value enough to allot them space on my overcrowded bookshelves.
I still have reservations about the intellectual property issues involved in the Kindle, and the level of control that Amazon has over the content, and I'm very annoyed that the download-able e-books offered by my public library work on every device in the world except the Kindle. I also think that for certain favorite authors whose books I've collected in print I will continue to buy physical copies. Despite these things, I now consider myself an enthusiastic fan of the e-book reader.