what would you change it to then to see a difference?
Timings are touch and go. For serious enthusiasts mainly. Your not going to see as much of a improvment with lower timings. I think when I went was doing 4,4,4,12 vs 4,4,3,5 I noticed about 250/mb memory improvment. It lowers the actual latency as well. The biggest thing you can change is overclock your CPU and actual ram frequencys.
For example my G.skill @ 4,4,3,5 with a E6600 @ 2400Mhz had memory read around 7,300mb/s @ 800mhz and with the same E6600 overclocked @ 3600Mhz the memory read increased to 10,228mb/s @ 800Mhz same timings and ram frequency just a higher cpu clockspeed. I think my Latency acutally dropped from like 57ns @ stock to 51.8ns @3600Mhz.
I have not messed around with the actual frequencys to see what kind of increase I can expect at say 900Mhz yet.
Download Everest or Sandra benchmarking apps. There a synthetic app that can test memory read/memory write/memory copy/ and memory latency. Just make mynute adjustments and run a benchmark and see what the preformance increase or decrease is. Also be sure to run Prime95 to test the stability of the new settings. It may boot up but if you run a blend test in Prime95 and it starts giving errors the timings are bad or the frequency is to high. You can try bumping the ram voltage to increase stability just be careful you can fry your ram.
I explained the actual terms in some thread but i'm not looking for it now. My advice work on your ram frequencys and overclock your cpu your not going to get a huge impact in timings. I don't recommend messing around with these until you have a good understanding of what they do and how they effect your PC.