If you're an Nvidia graphic card user, if you tried to force enable Anti-Aliasing, you'll notice it doesn't do anything.
That's simply because AA doesn't properly work for BnS for Nvidia graphic cards.

AMD/ATi users don't seem to have this problem, tho. Lucky you guys, but if you want a better performance AA, read on anyway.
[Update: 2/16/2012] NEW and BETTER AntiAliasing Injector by mrhaandi. The SMAA Injector. Visit his official blog for more information: http://mrhaandi.blogspot.com/p/injectsmaa.html
Download link: https://sites.google.com/site/mrhaan...rhaandi_1.2.7z

Why is it better?
1. Performance surpassing the FXAA version. Provides AA quality equal to 8xCS at virtually no performance impact.
2. More Antialiasing coverage, where FXAA couldn't apply on certain view angles.
3. Which improves visual motion quality, providing smoother edges while you're in motion.
4. Reduce visual effects on GUI overlay vs FXAA.
5. 0 affect on blur.

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Installation:
0. If you have the old FXAA files installed, delete all of the related files. See screenshot here to know which files to delete.
1. Download and Extract the .7z file. You should have 2 folders and a readme.txt file.
2. Copy the contents inside \d3d9 to your BnS\Bin folder.
3. Open injector.ini with notepad or wordpad and modify "preset = SMAA_PRESET_HIGH" to "preset = SMAA_PRESET_ULTRA"
4. Save the file. Start up the game. Press the Pause/Break key on your keyboard to enable the SMAA mode. If you previously have FXAA enabled already, then SMAA mode would be enabled by default.
5. If you take screenshots with the PrtSC key, the better looking screenshots with SMAA applied to them are in your BnS\Bin folder. The ugly ones are saved in BnS default screenshot folder, which is MyDocs\Pictures