If you use SMAA antialiasing instead of MSAA you can also make the game run faster (than with MSAA).
It's meant to allow you to improve the look of your games and change the look and mood of it to your liking. SweetFX allows you to add SMAA anti-aliasing, sharpening and the ability to tweak the colour, gamma, exposure and more. So just what is Sweet FX ? Well Simply, Sweet FX is a mod built on the InjectSMAA shader injector, which allows you to apply a suite of post processing shader effects to your games. Sweet FX isn't alone in this area there are other shader injection mod tools, like InjectFXAA, InjectSMAA or FXAAtool, to name but a few, but the creator of Sweet FX says that it improves on all of these.
When gaming, do you yearn for better quality, do you want games to look more vibrant or have a better feel of depth, well now thanks to Sweet FX, all this and more can be yours.