Ok what do these commands actually do to your image quality.

[MTL]

WHen i type them i get a lot less FPS drop

heh you noticed too?
i have an ATI card so i did>
DisableATITextureFilterOptimizationChecks=False [or was it True....hmm dammit i forgot] and turned ATI Catalyst AI to "Advanced", and i got more stable FPS on max settings. Or at least it seemed like it worked.

[Frustian]

The first two seem like optimization commands, if the first one is off you would get more fps, but no discernible image difference, it's mainly for if the optimization stops UT3 from running.

The third one is turned on to fix the campaign videos from crashing your system, but I don't know anything else about it.

[jixmixfix]

WHen i type them i get a lot less FPS drop but what do these commands do in terms of image quality does it decrease the image quality?

[Engine.ISVHacks]
UseMinimalNVIDIADriverShaderOptimization=True
bInitializeShadersOnDemand=True
PumpWindowMessagesWhenRenderThreadStalled=True