The biggest benefit in natural user interfaces is the ability to attract and captivate users with responses that are organic with minimal learning.
Let's embrace our pocket protectors and go sci-fi for a few. Remember the touch screens on Star Trek? No one had to jump on screen and tell you when Scotty pushed the bar it meant he was giving The Enterprise more juice. We all knew in Minority Report when Captain John Anderton swiped and pulled he was navigating a virtual library of information.
With the ability for NUI to mimic the physical world, classes on using a mouse (the reason why Solitaire and Minesweeper were included in Windows) or knowing you're the world's slowest typer because you chose to take physics in high school instead of typing, are eliminated. One of our team members has a 1 year old who uses an iPad to draw and flip through images, using gestures to navigate that his parents didn't even know existed (BTW... it was the horizontal five-finger swipe: http://www.macworld.com/article/1163019/ios_5_new_gestures.html).
With great ease of use comes great responsibility, for designers. We'll talk about this more in the upcoming articles in this series on how you should and should not design your natural user interface.