If you've been (un)fortunate enough to actually have the Windows 8.1 install work instead of locking up your computer, making the upgrade impossible, you may be wishing you didn't. Apparently, the way the new update handles mouse input can be horribly laggy in some games. This is not a good thing at all, and I'm very glad I have yet to install it on any of the machines here at BCCHQ South.
In this case, according to a post on Reddit, the changes in the DPI framework have caused games that don't use Raw Input or DirectInput to get hit with a massive amount of mouse lag. Among the games that are being affected by these problems are Deus Ex: Human Revolution, S.T.A.L.K.E.R.: Call of Prypiat, Metro 2033 and some games in Activision's Call of Duty series. It also seems to affect hardware that includes mice products with a high polling rate and high DPI.