It's absolutely terrible in rhythm games like RockBand when video and input have a delta, and even worse when you add audio desync into the mix. Fortunately you have a few knobs in the game options.
That's different--quakeworld did client side prediction so your local side was updating with no lag (ie, move the mouse and your view would rotate with very very little lag, just like you were playing a local fps). The positions of players was lagged because their canonical positions were controlled by the server, but that manifests itself totally different than display lag.
I am not sure if you are trolling or remembering through rose glasses. you CAN play qw with such a ping but you would not stand a chance against anyone with a ping of 30. projectiles and players jitter all around the place.
I made a lot of tests with LCD TV input lag, and 30ms lag vs 100ms lag makes a huge difference in playability. At 120ms+ FPS games are unplayable.