In NVIDIA's Graphics SDK 11, there is a anti-aliasing method named Fast Approximate Anti-Aliasing. It's based on MLAA, but only long edges are processed, ignore some shapes. After we have the long edges, sub-pixel level coverage can be computed by an intersect test between edges and pixels. The coverage is used in AA blending. Then Timothy Lottes have developed FXAA II. The quality is lower a bit but accelerated. On Xbox 360 with 720p, the FXAA II takes less than 2.0ms.
From KlayGE 3.12, the newest FXAA 3.11 is involved. Current implement takes 0.1ms on GTX480. It reaches high quality AA with trivial cost.