Got mine on Wednesday, I've been using a K3 Keyboard for a long time, and before that a Sony PRS 500 and then 505.
The screens look about the same under normal room lighting, without the PW light on. My wife proclaimed the PW as being whiter, without me telling her which was which. My eyes seem to prefer the K3 as being slightly lighter, but I suspect that is because my K3 full refreshes each page.
I use an Octovo Solis book light for night reading, the PW blows that out of the water. I can set it nice and low and not bother the sleeping lady next to me, and the light is incredibly even, especially at low levels. I have noticed the slight shadowing on the bottom of the screen at high levels, but they disappear in sunlight, which is the only time I would use the light at those levels anyway.
Touch screen responsiveness is really good. and the screen resolution, while it will not be immediately noticeable, makes for beautiful font rendering. The original e-ink pearl screen is about 167 pixels per inch, the new one (based on 60% more pixels, it's a 1024x768 screen) is at around 213 ppi, and you can see the difference.
If they had included physical page turn buttons, like the K3, this would, in fact, be the perfect e-reader for me. I get annoyed at having to move my thumb all the time to tap the screen, and the page turns every time I try to brush away cat fur (which lies in a layer about 3 feet thick in my house).
Performance is good, ergonomics (other than the aforementioned lack of buttons) is excellent, and even better with the cover. It feels tiny in comparison to my K3, the missing keyboard makes a big difference in feel. But it's surprisingly heavy.
Battery life is still unknown, but leaving the wireless on for a day visibly dropped the battery level, and I doubt it could go for more than a week with wireless on.
Downloading my library from amazon was reasonably pain free and it synced my collections with no problems. Reading is the same as I'm used to, might be a little faster. With the default settings, there's some ghosting that builds up between the full refreshes. I've been using e-ink for so long that the reverse flash hasn't bothered me for years, so I may enable the full page refresh permanently.
Home screen is annoying, I'm used to 10 books a page, so going to 6 is a little painful, although the book cover art is a welcome change. I would still love a little more control over how books display in the home screens, including grouping books in a series together, preferably in series order.
X-Ray is nice, but I have trouble coming up with scenarios where I'd find it actually useful.
Turning wireless on and off is a pain, I would love for a top level menu option like I'm used to, since I perform this action multiple times a day, on average.
I'm very happy with the device, despite a few annoyances, and it makes a worthy successor to my K3 (with it's completely unused keyboard just taking up space and taunting me). The Kindle leather cover is well designed and I love the magnet-enabled instant on/off it allows. The light is light years (har har) ahead of any other book light I've used, including the wedge. Two thumbprints up.