AnandTech posted the second part of their Intel Core 2 Duo processor memory performance article:
In our previous article we compared the performance of DDR versus DDR2 on the ASRock 775Dual-VSTA motherboard and found there was very little difference between DDR-400 and DDR2-533. Overall system performance remained very close with either memory at their optimized settings on this particular board. Our initial results continued to prove out that running your memory at the highest possible speed at the lowest possible latencies does make a performance difference in applications such as gaming. However, in applications like media encoding or general desktop programs the differences are hardly significant. The single biggest impact you can usually make in improving game performance is upgrading your GPU, and for applications like media encoding and mathematical programming a CPU upgrade would be more beneficial than faster memory..