well the results for me are in, not counting pcmark because It wouldn't' install on x64 version of windows xp or maybe that was aquamark but either way I don't have either one of them wouldn't' and the other had an error I got bored trying to fix when installing.
I see almost no difference that couldn't be seen for each time you run a benchmark the deviation. I see nearly identical scores for 1 gig and 2gig ( that is 2x512 and 4x512) on my athlon 64 4000+.
I actually between the example pictures saw higher scores for 1 gig than 2gig by a negligible amount. I have seen higher scores for 05 and 06 than the pictures show i have numbers written down but they aren't much higher than the 1 gig.
I only seem to notice the difference in some applications and battlefield series games where they are ram whores.