Just accounting for the memory speed it seems to make a proportional increase in memory intensive applications.
Does the extra ram spead help in gaming or video editing?
Using NERO version 7 products, I can see measureable increases in performance. I spent over 40 hours this weekend capturing, editing and encoding video at different settings to measure just such performance.
If the application is performance limited by the hard drives, CPU or Video system, it obviously won't make any difference.