60 FPS is enough for Freelancer (as any other action game too, i suppose).
I feel negative effects only when it gets below 40-45 FPS.
Edit: Futhermore, ppl, FPS higher then that is just a virtual number. With LCD monitor pixel reaction time of.. ~10 MS and refresh rate of 60-75 Hz it WILL NOT SHOW YOU MORE FRAMES THAN THAT.
High "FPS" will only make your ship buzzling in space. Damn cheaters.