The difference between the CAS7-7-7-20 and CAS8-8-8-20 timings at 1066MHz is fairly minimal in the SiSoftware bandwidth test. Just a few hundred megabytes per second separate these two configurations. However when increasing the timings from CAS8-8-8-20 to CAS9-9-9-20, almost 2GB/s of bandwidth is lost.
The EVEREST write performance is completely unaffected by memory latency, as the CAS7-7-7-20 and CAS10-10-10-20 configurations delivered pretty much the same result. The read performance did suffer as the timings went up, though the margins were not huge.
The SuperPI results barely changed as the timings were increased. The 16MB calculation time just saw a 6 second difference between CAS7-7-7-20 and CAS10-10-10-20 timings.