Lower effective input latency, higher input smoothness (the latter perceivable probably only on displays with higher refresh rates). That’s of course only for USB input devices (gamepads, mice, maybe keyboard), as for other types of devices idk.
But do note that only some devices will allow you to do this. For gamepads, the site gamepadla.com has a bunch of OC results made by Windows gamers. For mice, I saw some threads on some forums at some point (my mouse is natively 1000 Hz, so I didn’t focus on this)
EDIT: But like the difference can be really perceivable, it’s not a placebo. Especially on something like 240 Hz screen, the difference between say 125 Hz and 1000 Hz polling is just jarring. But it’s rare a 125 Hz mouse could be brought up this much, usually its sensor wouldn’t even be precise enough if it was shipped at such low polling.
But for example my controller could be overclocked from 250 to 1000, but 500 was the sweet spot in how it felt, while at 1000 it was unstable with some lags from time to time. But 500 was working perfectly and felt smoother.
Also notably the PS5’s DualSense can be overclocked from 250 to 1000 Hz (people claim 8000, but apparently it’s actually a lie)
They still sell them at the pharmacies