The long-awaited Windows 8.1 update seems to have brought with it more than just a Start menu.
There are claims on Reddit that the OS update has also introduced some unwelcome mouse lag, with titles such as Deus Ex Human Revolution, STALKER and Valve games among those that are affected.
The problem apparently lies with games that don't use ‘raw input' for reading mouse movements.
Something about Window's relationship with your mouse has been altered (specifically, the Multi DPI improvement for multiple monitors) and this causes those games that don't read raw mouse data to become close-to unplayable,” the Reddit thread claims.
Hacking in Human Revolution is particularly unplayable with this issue. Reading around the internet for support, apparently Call of Duty is affected as well.”