AF??

I know AA and what it is all about and frankly AA is over rated. (just my opinion) but what is AF and why does Doom 3 go 8x on it? Is it needed? Just wondering.

AF = Anisotropic Filering. It is an advanced method of filtering textures, it decreases the "blur effekt" that bilinear filtering is famous for.

This link might give you a more precise answer with screenshots:
http://www.richleader.com/bargainbinreview_anisotropic-filtering.htm

It's basically a gigantic improvement over trilinear mipmapping and it incorporates a new process for rendering the far and near mip. It's pretty intensive on the GPU though... Trilinear filtering and maybe 2 pass Anti-aliasing are fine for me.