I recently got the Kindle Paperwhite, and as a longtime fan of e-ink readers, I can tell you that this is the best eReader I have ever used. I'm not going to bore you with an in-depth review because there are so many places you can go to learn more. (Here's a link to Engadget's review of the Paperwhite.) Instead, I'll just summarize the features I like best about this Kindle and call it a day.

What's cool about it?

The size. The Kindle Paperwhite, as you can see from my side-by-side photo below, is smaller than the Kindle Keyboard (3rd generation Kindle) and the iPad mini. It fits the hand perfectly, like a small paperback book.
The touch screen. Every time I've watched someone use a Kindle, no matter which generation of the device, it doesn't take long before they try and touch the screen to navigate, even on devices that didn't have touch. The touch screen on this device "feels right," if you'll pardon the pun. It's more responsive than the Kindle Touch was, which makes a huge difference in the overall reading experience.
The built-in light. As far as I'm concerned, the Amazon case with built-in light was a must-have accessory for the Kindle Keyboard. On the Paperwhite, the light is built right in and is much easier on the eyes than any modern tablet. The light shines from the front of the device; it isn't lit from the back like other tablets. For some people, reading on a tablet is fine, but for me the light on the tablet screen pushes me out of a story after about an hour.
The battery. Amazon touts 8-week battery life. (You can get longer times if you are in the habit of disabling Wi-Fi.)
X-ray. X-ray isn't exclusive to Paperwhite. The Touch, Fire, and Kindle apps have it, but it wasn't available on the Kindle Keyboard. X-ray makes it easy to learn more about characters in a book by showing other passages where the characters are mentioned.
Whispersync. Whispersync isn't a feature exclusive to the Paperwhite either, but it's great. With Whispersync, you can start reading on your Kindle and pick up where you left off on your smartphone, tablet, or computer. It keeps your reading experience in sync across devices.
3G. This option isn't standard, but if you travel you may find it well worth the extra cost. The Wi-Fi only Paperwhite sells for $119, the 3G version sells for $189. There's no monthly fee, no data plan, and no limit. You can be anywhere with coverage, buy a new book and start reading in seconds.

I could go on and on, but if I did that, this would become an in-depth review. Let's sum it up by saying this: If you love reading, I am certain you'll love the Kindle Paperwhite.

Learn more about the Paperwhite at Amazon.