Notice that just getting a thread scheduled every 2 ms is already impossible for Windows, certainly one running a game. You'll get a bunch of outliers within the second. So even if you got your keyboard down to 5 ms, great, but you are not running an operating system that can reliably do something within that timespan!
Maybe I'm not understanding, but that doesn't seem correct.
Most people (gamers) are running mice at 500/1000Hz polling rates and you can easily verify the movement made in each 1-2ms update. (And it is most definitely a noticeable difference going from a standard 125Hz rate to even 500Hz.)
The mouse measuring data every 1-2ms will increase the quality of the motion tracking, but it won't necessarily help you with latency unless the data gets to the game fast and the game handles the data quickly.
This explanation by John Carmack comes to mind... it's a good reminder against a lot of the hardware fetishism that is mixed into otherwise good advice about gaming setups. https://superuser.com/questions/419070/transatlantic-ping-fa...