I compared the Paperwhite that I received with both my Kindle Keyboard and my Kindle Fire (1st generation) that I use for nighttime reading.
When there was no light on, the screen was very similar to the Kindle Keyboard, but with the light on, I - and some others who looked at it - had the impression that it was not as sharp as the Kindle Keyboard.
For nighttime reading in an unlit bedroom, the Kindle Fire won on sharpness, hands down. It was also much brighter, which is fine for me. So for me the best option was to keep my 2 old Kindles that I already had and send back the PW.