I installed Ubuntu 15.10 (upgraded from 15.04) on the XPS13 (9343, Windows version). As this ultrabook has a very high resolution touch-screen (3200x1800), I followed some useful threads on how to fix the resolution problems. As an example, here it is simply explained how to increase the font size in UNIX, and that work perfectly for all UNIX's windows. It worked also for Firefox's text, bar and tabs' names, but the "check boxes" and some other features are still tiny.
An additional problem that I can't solve is that the font/objects size in the programs I use is still very small (see example below). Also, my cursor has usually a normal size when moving on UNIX's windows, but when it goes on some other programs' windows, it becomes way smaller (you can see the black arrow in the Skype window).
Any hint about it? I'll be happy to provide more details if needed.