To us nerds it is (I paid £2,000 for the 4K telly with the - at the time - lowest response times, after initially only wanting to spend about £800 but then finding out how much higher response times were on 4K TVs compared to my old faithful Sony KDL 1080p TV - which I only bought for the response times)...
But, to normal people (my missus, every family member of ours) - they don't notice 100ms (I hooked up a PS3 through two ports, the Xbox One TV input port which is delayed by about that much, and then direct to the TV, to demonstrate the lag just on the XMB - and they were completely oblivious)...
For all of us, though - especially playing a game that's already laggy (now they've bumped up the server load) - I can't imagine playing outside of "game mode" etc...