I love how it retains and enhances touch and motion controls, the whole device is a perfect balance of features and power (motion controls better than Wii's, touch controls better than DS', better rumble than GameCube, more powerful than Wii U, most likely better online than 3DS and Wii U due to paid service, etc) all on a portable package that can still be played on TV.
It really seems to have the best of all worlds, and furthermore, the library is nigh-guaranteed to be the best of any single platform Nintendo has developed, by virtue of being their only focus, and yet still being ridiculously powerful for a portable device (the 3DS had all their focus for this year, but it's severely underpowered)