Originally Posted by Kazumi
I wonder how hard that is to make ingame available (for the programmers) if it isn't already.
And also how, say, 2.7x DS + FXAA compares to their MSAA implementation performance-wise (2x2 looks a bit overkill at least for playable)
MSAA has been around for some time. MSAA is relatively fast, but the full screen shaders so frequently used now days create artifacts, and it doesn't work at all with deferred shading (which is used in some recent AAA games), so FXAA has seen more usage lately. FXAA is simply a pixel shader effect itself, so it's pretty easy to implement and it runs well on recent hardware (faster than MSAA). The game has to be designed for FXAA, otherwise it makes everything pretty blurry unlike MSAA. If you want a technical description, check out the nVidia white paper
I should also mention that "injection" seems to be a hack that enable FXAA for games that don't natively support it. The quality will typically be worse than MSAA, or that of a game that actually supports it.