Mr. Aonuma has been very proud about showcasing the Zelda U demo, and just a few minutes ago he took to Miiverse to share his thoughts and answer a few questions about the demo. Below is the full screen capture of the comment:
The most interesting things to take away from this message were that the footage was actual gameplay, which many were claiming it was not. Also, the theme of exploration seems to be emphasized even more with the mountains in the far corner of the demo actually being able to be scaled.
Zelda U is shaping up to be THE game of 2015. Stick with Nintendo Enthusiast for more E3 coverage as it happens.