Corsair just published a detailed Application Note on memory performance. The pdf is posted on Corsair's Tech Notes page.

Memory modules are currently available which support a wide variety of different speeds and latency settings. Speed is easy to understand - in general, faster is better. But what do the latency settings mean? And, what impact do they have on memory performance? This paper will provide a brief background on latency settings and what they mean. Then, we will move to the lab, where we will run a suite of benchmarks over a wide variety of latency settings, and we will measure the impact of these settings on benchmark scores.

Check it out