Oh I agree, I just haven't bothered to try for more since I guessed 2666mhz with 12-11-11 timings would actually be faster. I have seen others doing 3333mhz on these with looser timings.
I really didn't spend much time overclocking it, and £109.99 3000mhz RAM is about 40% more expensive, I don't think its money well spent. I have simply set it to the settings above and just left it since then, same as I could probably do more than 4.4ghz, maybe one day i'll give it a go.