Very nice work but...
The main advantages of this technique is perhaps more pleasing results to the eye, no blurring of texture due to AA
Texture blurring due to AA? Post-process AA maybe but not MSAA, and even with PPAA there are stencil techniques to mend that.
the whole screen and also few pixels used to draw the AA geometry.
True, and you forgot to mention that memory requirements are reduced (so thumbs up there), but the geometry shader takes quite a bit of power compared to other shader functions. According to nVidia: "Only use the geometry shader when you REALLY need it"
Also, shaders operate by blocks of pixels, not individual ones. This means that if you draw a dot on screen one pixel wide, the effect is also being computed for the other 15 pixels around it (this is for a newer card I belive). So if your geometry is very complex or the scene is filled with edges, you will have a LOT of excess overhead.
Its a good idea, but not sure how practical it is. I like the direction though.