I have one, and I like it quite a bit. People talk about it as if it'll replace regular books, with comments about their smell, etc., but it doesn't replace them at all. If there's a Kindle version of a book I want to buy, then I go that route, but I have a pretty good backlog of paper books to read, and if I find a used o discounted paperback that's cheaper than a Kindle edition, I buy that.
It's nice to be able to carry around so many books at once, and I like the option of getting to read a chapter before buying. Another benefit that I rarely see mentioned is the "Save for Later" option. If you're browsing the Kindle store on it, and you see a book you want, you can add it to your "Save for Later" list. I used to go to book stores and see a book I'd want, and I'd be tempted to pick it up before it sells out or goes out of print. But Kindle books don't do either of those things, so you can add them to your saved list and wait to buy until you're ready to read it.
I have 40+ books on my saved list that I might have been tempted to buy in stores or Amazon ("only two more in stock! order soon!"). So it's saved me money and space in that way.
You can also put most public domain books on there for free. It's not much different from other e-readers in that way, though a lot of them are offered in the Kindle store for free by various organizations, which makes finding and downloading them easy. Take
Twenty Thousand Leagues Under the Sea, for example.
Also, there are promotions on there all the time, especially if you read genre fiction. When a new
Dexter book comes out, for example, they'll give away the first novel for free, to get you hooked.
Perdido Street Station by China Mieville,
Manifold: Time by Stephen Baxter and
The Briar King by Greg Keyes are three current examples. Amazon makes these offers fairly often.