If the service is decent enough with servers close by, it really isn't bad at all. In a PCgamer test, the input latency for Metro Exodus and Destiny 2 went from 46ms and 51ms local to 96ms and 75ms from GeForce Now, and 179ms and 129ms from Stadia.

For comparison, back when Tekken 7 was released on the PS4, it had 120ms of input lag.