So the Fire Strike Ultra testing showed a 13% gain over a 980Ti SC+ with the 1080FE.  How did Metro fare?  Same settings for the test, 4k:

Results, again mediocre.  This time about 15% gain.  The story here though is the minimums which did see a much nicer boost of about 27%:

So far not so good.  I think the pattern is set and the conclusion can be drawn.  Do not upgrade from a factory overclocked 980Ti to an FE 1080 even for 4k.  The testing will continue, but I don’t expect dramatic differences will be found.  Still, a gain is a gain and the card is running cool and quiet with reduced power gain.  Also, I see no sign of any thermal throttling that actually impacts framerate.  There is just no scenario where the GTX1080 FE is falling below the 980Ti factory OC performance under any circumstance, so that is some good news.