We've released a new build of System Shock 2 on Steam this evening that will provide improved support for fan made mods, stability, and the ability to update to the latest SS2Tool from www.systemshock.org
The ability to play fan missions has also been added so head on over to the excellent guide written by Saleck to get the most from this feature.
http://steamcommunity.com/sharedfiles/filedetails/?id=144318168#53863
If you wish to mod the game, the installation folder will have to be placed somewhere other than "C:\Program Files"
We've also re-enabled the original intro to show some love for Irrational Games, and Looking Glass Studios.
Many thanks to ps47.3dfx and Saleck for testing, suggestions, and providing support for this release.