Like some others, when I initially saw the screen out of the box, was concerned about blotches etc. but truly, after trying various lighting scenarios, playing with the the fonts etc. came to the conclusion this is one *incredible* product! It is hands-down the best Kindle I have ever owned (including the K4). The contrast and screen are amazing. My sister has a K3 - -we held them up side by side and she wanted (and ordered!) a Paperwhite on the spot.
Try out the PW in various places you frequent (Starbucks, florescent lighted break-room at work, airplane, bus ride home, in bed etc.). After a bit of experimenting/adjusting I love the PW and will never go back to a non-lighted screen again.