I heard that people were/are getting annoyed by "Ghosting" after the 1.5.0 update so a threw together a simple screen cleaner to get rid of the ghosting manually.
Basically it is two images, a pure white wallpaper sized image and a pure black screensaver sized image.
The concept is simple, put the nook into screensaver mode and the screen will turn black and then press the power/hold button again and it is white. Repeat as much as you like.
Get it here:
http://www.fileserve.com/file/J3SaBzs
Read the readme text file for directions.
~Shades