If you're having constant 60fps in game and notice stutters, try turning off GOG Galaxy overlay.
It fixed it for me. It's a whole new experience in game.

Yeah, I had the same issue. The game would lag like crazy when moving the camera while moving. Disabling the overlay before launching the game results in smooth gameplay.

(I never had 60 fps in the first place, though, because my system isn't powerful enough for the settings I use -- but I'm perfectly happy with just 30 fps. :p )

I had the exact same problems, RIGHT AFTER installing GOG Galaxy. I never did before. After confirming that it was indeed the problem--and still persisted even after deactivating "GOG Overlay", I uninstalled GOG Galaxy altogether, and THIS SOLVED THE PROBLEM! No more sound stutters and lagging crap.

One thing still a mystery for me is, what the eff was in that 12GB update???!