I set a profile for the game in AMD Catalyst. I put all of the settings to use the application defaults except for forcing vsync with triple buffering so my FPS is kept at what the monitor displays. I checked it with FRAPS and this is working perfectly. nVidia control panels should offer similar options.

Unfortunately, I cannot get multiplayer to work and am getting very frustrated with it. First off, the game does not accept the multiplayer key that I got from GOG. When I try to enter it in the miscellaneous options panel the OK button is disabled. There are no helpful stickies or guides here to explain where to even start, and do I install the map pack loose in the map folder or in the Scenarios subfolder?

Yes, it is. It works for me.

In the registry go to this part:
HKEY_LOCAL_MACHINE\SOFTWARE\Shiny Entertainment\Sacrifice\Options

Then there's a D-WORD there called "Target framerate". Default is at 30 (change to decimal) but you can probably change it to whatever you like however the engine might start to act funny with unusual numbers. I recommend 60 but I don't think you can change things in-game settings after that so that first before messing with registry. I'm not sure about backups in case things go wrong but as long as you keep the default numbers written down it shouldn't stop working all of the sudden.

This is from the manual: "[i]TARGET FRAMERATE
This slider allows you to change the target framerate in the game. By adjusting the framerate you can find the
best balance between level of detail and frames per second on your machine. The recommended and default
setting is 20 frames per second. This allows for high playability with a high polygon count. (Note: Setting at
20 fps does not limit performance to 20 fps)[/i]"

Notice the last sentence?

EDIT: I just noticed this thread was from 2012. Whoops.