Fhi, Kelimbror, Cowt you are all right. Some people/games seem to need to turn in-game anti-aliasing off to be able to see any effect of SweetFX. This is also mentioned SweetFX readme file:
I added note to my comment above + pic where this setting is.Q: I don't see any change in the image
A: Try turning off anti-aliasing in the game (not in the mod)
The mod is not compatible with some antialias implementations.
It might be made compatible by setting compability flags.
If not then you can always use the included SMAA anti-aliasing.