Hello! This is my first Kindle, and my first touch-screen electronic device (I have clearly been living in the Stone Age!), so you experienced e-readers will have to read my review with a bit of a jaded eye.
The Paperwhite is incredible! I received the 3G model with ads. My husband was very skeptical about the ads, but they haven't bothered me at all. So far I've only seen ads for books or video games, and they only show up as my off-screen "screensaver" or on the store page; the later of which you would expect if you shop at Amazon at all. Having the 3G is terrific; if I finish a book and I need the sequel ASAP, it doesn't matter if I am driving through rural Connecticut, on a ferry in the Long Island Sound, or somewhere where the WiFi isn't free. I can just grab the book I need whenever I want.

That makes a book-addicted, shopping-addicted gal very happy indeed.
The Kindle PW that I got has no mechanical/electrical flaws so far, as well. The LEDs are bright and fully white. The battery lasts quite nicely (if you have the light below 10, that is. I tend to leave the light on closer to maximum, then the battery only lasts me a day and a half, rather than the touted 8 weeks.) The screen and skin prior to protecting them with add-ons are nice and smooth and clear. Even with my contacts out and my super-close-up vision on, I can't see any pixels. The e-ink or whatever is very black and very smooth. It's surreal, almost; better than the printed page and better than a computer, it almost floats in there without moving. It's sorta, holographic I guess, but not in the bad staticky Star Wars hologram kind of way.
The controls for turning forward pages, going back pages, getting to your "home" page and other settings, and changing the lighting is terrific for a new user who hasn't used a touch-screen before; very ergonomic and easy to get to know. My very, very favorite feature is being able to hold your finger down on a word and having it pop right up in a dictionary on the screen! Try doing that with a book! I'm quite a logophile and while I hardly look up words, I've found myself using this feature regularly now that I
can. It was especially fun and helpful when I was reading
Life of Pi, there were a few animals I was unfamiliar with and thanks to the dictionary feature, I didn't have to wonder what they were or how they looked as I was constructing the scenes in my mind.
I won't be using the game/active content abilities much, but my husband and kids have already made great use of them, and I find the same surreal clarity and smoothness in the graphics for games and illustrations in children's books as I find in the text. Even Wikipedia photos are incredibly clear!
Overall, while I can't compare the Kindle PW to any other devices, I can say that owning one has been a fantastic experience and I'm looking forward to not
needing to compare it to anything else for a long, long time to come. This will be the only one for me!!