Actually, there are only a couple.
1: Go into your nvida control panel, make a game profile for shattered horizons, set Pre Rendered Frames to zero, that smooths out a lot of stuttering.
2: Again in the nvidia control panel, if you are using SLI (2x 8800gts 640's here) set your SLI rendering mode to force alternate frame rendering 2, unless you have the latest 257.15 or higher drivers, in which case its default anyway.
This next tip is not for nvidia cards, its for anyone with a core 2 processor (i dont know if it applies to later intel processors, as i dont have one).
My motherboard has an a couple of options in the BIOS for processor throttling, such as C1E enhanced halt state, and EIST (enhanced intel speedstep). When these options are enabled, it renders the game completely unplayable, with massive stuttering, as soon as i disable it, smooth as butter, so if you are having massive stuttering issues, check your motherboard bios throttling options, turn them off and see if that helps.
EDIT: The reason for changing the C1E and EIST for me is, with them on, if i have cpu-z running while i'm playing sh, it shows my clocks bouncing back and forth from normal to half, it may just be an error on my hardware, but it cant tell if i'm playing or not for some odd reason.
Also, please please do not change any other settings in your bios unless you know what you are doing, as you could make your computer not boot, and then you would have to figure out how to reset the bios, which can be a real pain sometimes.
Let me know how it works, i hope this helps some people with their FPS troubles.