Pottering WordPress themes for years now I have started fumbling around with child themes. And this Twenty Thirteen really surprised me. What an awesome starting point to explore.
Like always I am overdoing everything to the point of being merely idiotic instead of delicate. So as a personal playground it will probably not last very long.
Seriously: this really feels like a breath of fresh air. Though I wonder if it will serve its purpose as a default theme.
But this is true: it looks great (cool) on any device.