the problem about the trees is the retarded mass-useage of Alphatextures, every bush or tree is a bunch of transparent layers. The only way to fix this is to use supersampling/transparency supersampling on them. But that is a HUGE hardware drain in this game since so many layers are used.

If they could manage to make their own filter for this game it would be nicer.

If oyu are ok with a lil less "depth" you can enable full screen MLAA (force it via ati software). Or soon with nvidia FXAA option (i guess next driver perhaps if we lucky).

This is far less gpu drainish

2X Supersampled looks a bit better but 4X is needed to make the tree flicker go away. Sometimes also the graphic driver version is more "flickerish" then others.

but 2X 460 should work with 4X supersampling. But im not 100% sure if that is the problem with what you explained...
give it a shot. Perhaps it helps.