The strange thing is, as far I know, that Windows-8 should behave the same way like Windows-8.1. Earlier Windows-Versions are different, from what I looked up. Based on this, drivers are most likely the issue. Some people got it after installing an AMD-GPU, which points towards driver-issues as well and got several times confirmed, that other drivers fixed the issue for some people. The last thing you could try, would be to do another clean Windows-8.1-Install and double-check the behavior before and after you install something additional. Could try a different mouse as well, to see if a different mouse + driver-combo would change something. If a game doesn't support raw-input, then you can't do much. High polling / dpi can create some lag as well if your system can't keep up with it. I double-checked my wife's system (Windows-8) and everything is fine there as well. She uses a Roccat Kone[+]. Otherwise I have no other ideas, sorry.
For some reason I feel like the new DPI features of Windows 8.1 have caused these issues. As far as I know, Mouse Acceleration is determined by DPI... so maybe games are detecting DPI weirdly or Windows has a bug in itself that's causing these problems. Regardless, I'm definitely still leaving it as a "Windows 8.1 issue" because I don't have the problem in any other Windows OS or Linux for that matter. Hopefully it gets fixed someday. Staying on 7 for now.
Not "directly" related, but the only mouse-related problem I have in 8.1 is my graphics tablet. Taps like to stop the cursor still and then release it a short time later. Under normal circumstances, this isn't an issue, but on the game I play (osu!), it becomes a problem when I need the cursor to update its location quickly and consistently. I believe Windows 8 was the same way. Windows 7 is flawless in this regard.
I would really suggest to try a different mouse plus the driver / software it comes with. Just grab one from a mate or so. The issue seems only to effect certain setup's / games and even my TOG-mates still recommend Windows-8 over Windows-7 for gaming. For Windows-8.1 I can only speak for myself, as my TOG-mates will not go for it as long it's not out officially.
These updates seems to have fix my erratic mouse and mouse lag. I can now turn off Enhance Pointer Precision and still have controlled precise movements.
Oh god I'm soooo excited to hear that. Once I hear a few more people confirm, I'll roll out 8.1 to my desktop again. Can't tell via VM or Laptop too easily.
I haven't tested too much yet, but the GA rollup feels smooth as silk. I've not noticed any lagginess at all
Can't say I've notice any real difference with the GA roll-up, but in any case, nothing (that I've noticed) got worse Didn't have (or notice anyway) any mouse issue in 8.1 before the update, don't notice a difference after it. I have a Microsoft Comfort Mouse 6000.
I'm on the public version of 8.1 now and the mouse problem is still not fixed for me. I think it is a USB problem, initially I thought it was just the mouse rate app that was bugged but that's not it. The mouse rate won't go past 166Hz no matter what and is extremely slow in games. Tried both USB 2.0 and USB 3.0.