I am using GeForce Now and it works perfectly fine for single player games. The problem is any game that requires very fast feedback and/or is multiplayer seems to be totally dependent not on the service, but the quality of service from you ISP and the DNS routing employed.
I abhor where game publishers really want to go with this but, highly doubt they have the acumen to lobby in the US to bring internet infrastructure up to snuff, so thankfully this won't be replacing multiplayer games and racing and flying games any time soon.
"Meet the new Boss, same as the old Boss." - The Who.