In motion I don't notice them, besides AA really kills performance. I'd rather up the texture quality/effects than AA
If it's going too slow for anyone there's a line you can add in the console to turn off the HDR effect.
I'm running with 2xAA, all settings high except shaders set to medium. 1280x800 resolution. 45 - 70 fps on my early 08 MBP.