The main benefit I see from these is that I would expect 4k gaming to finally be a smooth 60fps (minus poorly coded/optimized games). Below that, a 1080 will run anything maxxed at less than 4k smooth as silk without sweating.
The challenge for Nvidia this series is going to be convincing owners that if they upgrade this is one of those gens that's really going to require a likely expensive 4k/g-sync/etc. monitor upgrade too in order to really take advantage of it. Otherwise a 1080 or maybe 1070 will more than handle 2k or less resolution. I know it's often the case that monitor and vc upgrades go hand-in-hand, but I guess what I'm saying is this is a gen where it is more necessary than usual.