Not to mention, that these are the GOG forums, not the official TW2 ones. To get the attention of CDPR go to http://en.thewitcher.com/forum/ and post there.

Is there a proper solution to this?

I've got a brand new computer (finally!! :)), GTX770, i5 4670K, the latest driver (335.32 or something like that), fired up the Witcher 2 (not been able to turn it on my old computer), and to my shock am experiencing mouse lag.

I am using the latest version of the game from GOG.