FXAA (Fast Approximate Antialiasing) should only be used in three situations:
1)MSAA+TRAA is not supported
2)MSAA/SSAA is too costly
3)Used as MSAA+FXAA to get rid of aliasing that MSAA/TRAA do not work on (in this case the FXAA strength should be dialed down a bit)
FXAA PPI version is easier to configure and includes extra, optional post processing filters such as tonemap, sepia, bloom, anaglyph 3D and vignette.
The inject tool features an even easier to use GUI, speeding up the time required to find the desired configuration.
Place all the files in your main 2K12 folder
This is my setup
http://dl.dropbox.com/u/4689865/injFxaaSettings.h
Place this in the injFX_Shaders folder
Some pics:


