This tweet from Linda Stone about the iPad is right on:
iPad is the iPod of reading. A sense that distractions r minimized. Only what’s essential in the experience.
This goes beyond iBooks. The iPad is different than a traditional computer in that you are limited to working within one application at a time. The entire screen is always devoted to the task at hand. Distractions from other applications are minimized. Valuable focus and attention are maximized.
The iPad excels at content consumptions, but its potential for content production is untapped.