We got our hands on a Vita running the newly announced manga/comic reading Reader software today at TGS.
The first thing I noticed is how great manga looks on the Vita's OLED screen. Colors seem to pop right off the screen and into your eyeballs, and black lines are sharp and defined. Color manga in particular is a treat. Every volume I flipped through was really easy on the eyes, and I had no problem seeing even the smallest detail.
Flipping through the pages can be done with the d-pad or the L and R buttons, but swiping the touchscreen feels more natural, and the accompanying page turn visual effect looks pretty slick. Hitting the circle button zooms the view in to the individual cell level, and continued presses step through remaining cells in order. Turning the Vita to a portrait view lets you use the L button to turn the pages.