The Reader, Wowio's blog on reading technology, takes another stab at it:
In my earlier specifications for an ideal ebook reader, I thought that a 12″display would be ideal. Now, after using a 12″Lenovo X61T Tablet PC, a 6″Sony Reader and a 3.5" iPhone, I’ve changed my mind. The high pixel density and high contrast of the iPhone’s display allows for good readability at reduced text sizes, and the weight and battery life penalties suffered by the Tablet PC make a smaller screen even more attractive. At four pounds, the the X61T gets to be uncomfortable while reading in bed, for example. A high-pixel-density 5.25″display — as conjectured by the rumor sites — would provide very usable screen real estate without unduly compromising portability or power consumption.