Very happy with the touch-screen XPS 13 and Ubuntu. Basically no trouble that I didn't create myself.
Specifically, I immediately tried to upgrade to 16.04 from the (working-fine) out-of-the-box 14.04, which failed, and then discovered that there was bug in the Ubuntu installer so it couldn't cope with the SSD.
But all work-roundable with pretty minimal googling. I might have been more worried if I wasn't used to setting up linuxes on laptops (first time I did it, I needed a framebuffer for the video. Tell that to 'the young people of today, they don't believe you.) But surely the same is true for pretty such anyone who would actually *want* linux on a laptop?
The only other real problem I had was video (working, but tearing), which all got better with xorg-edgers. Again, not difficult to solve with a bit of searching.
Since then, it All. Just. Works. So to speak. And it's very nice hardware.