I'm playing the current german version for a week now and it works like a charm. No major bugs, no crashes, no freezes. Meanwhile I'm flying the Freij Mk2 -> advanced game progress.
FPS drop only when screen is filled with big pixel masses e.g. just before crashing with another ship or sometimes while the planet landing animation. Gameplay, even in heavy spave combat, is flawless.
Some animations in the station appear to run too fast - people's movement or marquees, but space flight is not affected by that.
The only bug I experienced is a generic mission that I failed, which resides now in my mission log as a zombie forever. But I think this is no technical problem of the GOG adaption.
So - give it another try!
My system is Win7/64 with a 1st gen i7.