My ophthalmologist was quite impressed with the Reader's display and thought it would be great for his patients. We didn't discuss backlit screens, but is that enough of an endorsement for you to ditch your PDA, m-reader?
I ditched my PDA in December, and it was a great decision. I do think it's better for my eyes because I can enlarge the font more while still having a reasonable number of lines on the page compared to a PDA's display.