Pffff, I have my own theory on this whole thing...I think Intel's been withholding info about their chipset problem and that everyone is trying to fix something on SF end that cannot really be fixed, only maybe worked around. Way less issues in AMD camp and older systems with SATA-3 do not really report problem either, at least not nearly as frequently as H/P67/Z68s do.
So that leaves only three gaping holes in your (their) theory.
1. Why does the Crucial M4 simply just work? It has superior access times and over 500mb sequential reads. If it's a chipset limitation, the M4 would be running into it as well.
2. Why has 2.13 not working for everyone given what we know it does.
3. Why, albeit at a lesser rate, do other system like X58, P55 and AMD systems still experience the problem?
If you frequent OCZ forums, you'll notice that some users have noticed changes in the 2.13 firmware that OCZ did not release in their notes about it. When asked, OCZ replies that we can only tell you what Sandforce allows us to tell you because of the non-disclosure agreement.
At some point this issue will be fixed. And we'll never know what it really was. Sandforce is currently in bed with both OCZ and Intel. Intel's next set of drives will be Sandforce powered.