I have one of the first-gen (non Sputnik) systems. I simultaneously love it and hate it so much that after one year I had to put my (mixed) feelings in writing here: http://lorenzo.villani.me/2013/08/19/dell-xps-13-l321x-the-r... (this is little more than a pondered rant, unlike OP's thorough review).

However, I think this year I'm probably going to bite the bullet and buy a 13" Retina MacBook Pro.