Ok, here it is. I benched with 2x/4x and 4x/8x, both OC'd (400/850) and stock. Watching BenchEmAll run through Far Cry, I don't think the AA worked, so those results probably only reflect the performance hit of AF.
Even with AA and AF on, there isnt' a huge benefit to match the huge overclock of 400/850. The only remotely signifigant gain was 10FPS at 4x/8x and 1600*1200 in UT2004. I'm guessing this is because, at any less demanding setting, my computer has some hardcore CPU bottlenecking going on - not that these framerates are anything to complain about, though!