Cocoia Blog has a thoughtful analysis of user interface concepts in the iPad OS. 

The iPad’s UI is without a doubt the most fascinating thing about this device. The particular way it has been thoughtfully scaled up from the iPhone’s interface is impressive, shrugging off the filesystem and multitasking in favor of obvious modal interactions.

Aerogel is a manufactured material with the lowest bulk density of any known porous solid. It is derived from a gel in which the liquid component of the gel has been replaced with a gas. The result is an extremely low-density solid with several remarkable properties, most notably its effectiveness as a thermal insulator and its extremely low density. It is nicknamed frozen smoke, due to its translucent nature.

…! Don’t miss the photo of a 5 lb brick resting on a piece of aerogel weighing only 2 grams. It basically looks like it’s floating.