Anandtech analyzes the retina display on the iPad 3. Brightness and contrast are about the same as the iPad 2 and middle of the road compared to other tablets. Color gamut is a big improvement over the previous iPad.

But thing I love about the retina display the most is the example at the bottom of the first page. The show a side by side of how web browser text looks on the iPad 2, Transformer Prime, and the new iPad. It's such a dramatic difference. Reading web pages has gotten so much nicer because now it's rather easy to read even small font text on pages without needing to zoom in.

http://www.anandtech.com/show/5689/the-new-ipad-retina-display-analysis