Avoid the dell developers edition xps13. There's no end key, the trackpad is unusable. Even worse, avoid getting the windows version and installing Linux on that: the trackpad is even less unusable (resets to lower corner intermittently on clicks), and in order to get the wi-fi working I had to recompile the kernel driver telling it that it was FOSS.
For the most part these issues are all fixed in recent kernel versions (> 4.2). The default trackpad driver (synaptics) is indeed buggy, but the newer libinput driver (available in the Ubuntu repos since 15.10) works perfectly. The WiFi card is a bit annoying if you want to build the driver yourself but it works out of the box on stock Ubuntu 15.10.
Admittedly there were some issues early on, but now that issues have all been patched it's an excellent laptop. Fantastic build quality, great battery life, and the display is the best I've seen on a laptop.
