I'm not too impressed honestly. 120 fps is the minimum for me when it comes to playing games. Then again I was used to 120hz monitors on CRTs in the early 2000s with 0 input lag. I would only ever consider 4k for normal desktop usage but there's no way I would pay anything for 60 fps and we all know 4k monitors will be stupidly expensive for at least 10 years.
It always seemed strange that monitors aim for 60fps. That seems like a recipe for input lag. They could aim for 90fps, because when they fail to meet that, at least they'll still achieve 60fps. Then again, the audience of hardcore gamers who would notice that sort of thing is probably small, so I guess it makes economic sense.
It's not like modern games have that much CPU time to prepare each 1/60 sec frame -- 16ms actually.
As for input lag, they can scan inpput at different frequencies and adapt the next frame accordingly, but it's not like the input is gonna show in any less than 1/60 for an graphically involved game.