My Nook Glow has a similar issue but it doesn't bother me at all.
The Nook makes night reading a real pleasure and cuts way down on glare & eye strain vs other backlit displays.
The Paperwhite has some nice features that I wish my Nook had but the lack of a microSD slot on the Kindle is a dealbreaker for me (if I didn't already have a Nook).
I like to load them books on!