SiSoft Sandra doesn't really show us anything when it comes to memory performance.
Replacing Everest in our labs is AIDA64. This new testing suite is from the core development team from Lavalys and continues that tradition. The guys have thrown in better support for multithreaded CPUs as well as full 64 bit support. We use this to test memory and HDDs for now, but may find ourselves opening this up to other areas of the motherboard.
Looking at memory performance under AIDA64, you can see that write performance is just a little slower on our new 990FX board, but you can also see that read performance is up. Overclocked, though, you can see some extra performance again in read performance.