I dunno if anyone else did this, but I went into my xfire_games.ini file and put this at the end:
I derived it from a topic in Xfire's forums vouching for FS2 support.
LauncherDirKey=HKEY-LOCAL-MACHINE\SOFTWARE\Volition, Inc.\FreeSpace 2\1.20.000
Launch=%UA_LAUNCHER_EXE_PATH% %UA_LAUNCHER_EXTRA_ARGS% %UA_LAUNCHER_NETWORK_ARGS%
Changes are the LauncherExe (original used an OLD version of FS2 Open.. dunno if this makes any difference because I didn't wanna take chances) and added "InGameRenderer=OGL", where OGL can also be D3D8 depending on renderer (with my settings I have little to no difference because the latest MediaVPs don't work well with my POS craptop computer).
I have no clue if the registries are correct. What I ended up having to do was manually selecting the EXE. After doing everything, though, it all works!
Ingame works, too. I was testing out broadcasting last night, and even had some viewers.