While Nintendo may have struggled to explain adequately the Wii U's unique charms at E3, the machine was created with one principle in mind: to do what Wii can't.

Nintendo president Satoru Iwata told investors that while being an improved Wii — it does full HD output for a start — it's designed to be a brand new experience, saying:

We have designed and developed the Nintendo 3DS and the Wii U so that each of them is able to realize what has been impossible with the existing systems, and we believe that these systems will be able to offer consumers unprecedented experiences, in addition to providing them with improvements from the Nintendo DS and the Wii.

A 6.2" touch screen in a motion-sensing controller should take care of that nicely.

[source nintendo.co.jp]