Hi - I checked in with some graphics devs and I'm told the underruns don't really get fixed until 4.10 - and none of the current or imminent 01.org updaters will pull in the driver from 4.10 as that is only at the rc stage, so they won't fix the underrun problems.
If you're still seeing flicker in the 4.10rc series, you can help get the bug(s) fixed by reporting them as detailed here:
https://01.org/linuxgraphics/documentation/how-report-bugs
Just got my Late 2016 Razer Blade Stealth QHD and installed Ubuntu 16.10 on it. Aggressive screen flickering at native resolution. Upgrading the kernel to 4.10rc4 and installing Intel Kaby Lake DMC firmware make this less aggressive/more usable but I still see the flicker occasionally. dmesg shows: [ 182.918947] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] ERROR CPU pipe A FIFO underrun Installing+running Intel Graphics updater for linux v2.0.3 does not help.