I see the regular confusion here. The response time is NOT linked to input lag. This mix up seem to be as common as "you need 100 hz for gaming notion" when it comes to television that don´t even support 100 hz interpolates which add graphical errors and input lag
As for input lag it´s very real. When I was on my 60 ms input lag sony TV I could never get nowhere close to my best lap times on my previous CRT. I had no idea about input lag back then. I was finding it amazing to run on a big 32" tv but for the heck of me for a year or two I never understood why I never regained the speed I had on the CRT while having more fun. Response time on that wasn´t that great either 16 ms but that I could get used to as a form of motion blur.
My current Sony W6 is faster but still have problems with trailing with it´s 9 ms panel but for those that never used CRT or don´t have a plasma may not react to that. Plasma is not quite as good as CRT either despite not having the response time issue it´s indefiniatly faster then LCD.
So yes I would say it´s proven that input lag matters for me in actual performance.
Now again remember response time is NOT at all linked to the delay before you see the reaction of your control inputs on screen. With lots of input lag you are always some frame behind and just can´t react fast enough to slides and you botch corner entries and escapes particularly if you have uneven input lag. Where you sometimes are at a respectable 20 ms and then go to 70 ms.
From my finding 20 ms on the monitor side less then so I don´t feel severly handicapped. If you are constantly under 16 ms you are seldom a frame behind and need to find another excuse for your short comings
But the input lag is not just from the monitor so always the lower the better
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I run a lot of pinball beside simracing and the occasional fps so yes it´s incredibly noticable. Actually I did sense it on my old tv playing fps as well but I didn´t figure it would effect my simracing like that at all. Another tip don´t run v-sync as it adds on the input lag when the GPU waits and don´t through out the renders as fast as it gets them.