There is a misconception that there is a power management issue on the XPS13 QHD+ machines with the latest kernels. I can confirm that there is an issue with the intel driver which affects both the XPS13 9343 and 9350 models with a QHD+ display. A quick rundown on my symptoms with my 9350:
With kernel 4.2 on Ubuntu, I can boot to X but I can not get my display working after a resume from standby. After a resume, there is no backlight at all, but the operating system is still running.
With kernel 4.3 on Ubuntu, when I boot I get a black screen with a backlight, but nothing else. To bring the display up, I suspend the computer either remotely through ssh, by closing the lid, or by pressing the power button once. These suspend methods are of course relevant only to my setup. Once I resume from suspend, I am greeted with my desktop environment as the display activates correctly.
I have found a temporary fix for now until the fix gets pulled into a distribution kernel. The fix resides in a drm-intel-nightly build of the 4.3 kernel. I am currently booting with 4.3.0-994-generic. I got it from kernel.ubuntu.com/~kernel-ppa/mainline/drm-intel-nightly/2015-11-03-wily/ . As of right now though, the two architecture specific header and image files are not available. I saw this yesterday as well. I think if you keep checking, a successful build will finish and you can download a copy of that nightly.
On my 9350 (with skylake) when I was installing the kernel though, I ran into an error that said I was missing skl_guc_ver4.bin. To satisfy the dependency, I downloaded the original archive which is used to make firmware-misc-nonfree in debian. In particular, I downloaded the orig.tar.xz file from packages.debian.org/stretch/firmware-misc-nonfree, extracted the skl_guc_ver4.bin softlink and skl_guc_ver4_3.bin binary file and moved them to /lib/firmware/i915/ . I then had to run update-grub in order to regenerate my initramfs so that the firmware file would get included. Again, this step may be completyely unnecessary on a non-skylake machine (9343).
Let me know if this helps anyone. I give most of the credit to @dmcrtr as he filed a bug report at launchpad and had someone help him to find this kernel to try on his 9343 QHD+ machine.