I've always been a M+KB player and especially for FPS games I've always found it impossible to aim with the sticks, so the trackpads really helped in this regard. Especially for older games that may not natively support joysticks it was a game changer (I recently played Riddick: Escape from Butcher Bay)
It's hard to imagine quickly centering onto a headshot pixel (or group of maybe 12 pixels) with a trackpad. Especially if the target is moving.
I'd like to see a video of someone demonstrating real in-game use of these trackpads on different types of games. None of the reviews I've seen so far go into any detail on it.
EDIT: I found the trackpad usage detail I was looking for. But it's not using the new controller, just a steam deck. Looks a lot more accurate than I imagined. https://youtu.be/0BQEg3puMsc