On Witcher 2, I experience and have always experienced terrible mouse lag only on menus and similar situations (dialogs, dice poker, anywhere I need to "select" something with the mouse), and this always happened, with all computers where I played the game, even on different Windows versions.

Admittedly, I never played it on a high end gaming rig, but I always have indications that the machine is capable enough. I'm running it with low specs to prevent lag in-game, so using the mouse to rotate vision runs fast and fine, graphics look sharp and all, combat controls are quite precise. I'm not sure about my FPS rate, but it seems to hold.

The mouse doesn't stutter, it simply drags slowly behind my hand movement. It does get to where I wanted to point, but only after I stopped moving, which is extremely annoying. It doesn't look like something about mouse sensitivity, it looks like a deliberate smoothing effect.

My current specs:
- Intel Core i7-3770S 3.1GHz
- 8GB RAM
- Windows 8 x64
- AMD Radeon HD 7650A 1GB (yes, it's the weak point here, it's an All-in-one card, should compare to laptop GPUs)

I looked over the internet, and tried everything:

- Reduced specs to lowest
- Turned off V-Sync
- Changed mouse sensitivity to max and minimum
- Editted user.ini (Smoothness=0, MouseSmoothness=0, SensitivityX=0, SensitivityY=0)
- Tried messing with Windows mouse config, activated an improved precision option

None of this yielded any noticeable change.

This is annoying to the point of unplayable.

Anyone know what I can do to fix this?

GPU is weak alright, but why does it drag only when on menus and on bloody dice poker?

Any suggestions on how I can measure FPS and get a video out of it?

By the way I didn't reboot after making changes, will try that too at home.

Yeah hardware mouse is not enabled in W2 that explains the slow mouse drag, especially if your gpu doesn't require the minimum specs. You can try playing with 360 controller which works really nice with this game...
Download fraps to measure your fps, it's a free app :)

It can't be fixed, only improved slightly by lowering all graphics settings and/or playing on a powerful PC. As stated above, the game uses a software emulated mouse cursor which is slow and sluggish, even if you surpass the minimum requirements. It gets worse the higher your graphics settings and resolution are. I would guess this is a side effect of making the game controller-friendly. In fact the user interface as a whole gives the impression that they were preparing for the console port and wanted to make it go as smoothly as possible.