Does unity support TXAA antialiasing?
Its a new type of antialiasing for geforce 600 series.
No unity only supports 2x, 4x and 8x multi-sampling.
In addition there are Antialiasing (PostEffect)
You are free to code it yourself 
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(Im personal hoping for TSSAA = Transparency Super-Sampling Anti-Aliasing)
You can’t code this yourself… it’s a feature of the GPU…
It may be accelerated by the GPU but the algorithm can be used on CPU side too (But its not very fast, and you have to code it yourself).
Nvidia does have FXAA support in there control panel but the unity Post effects does have FXAA too.