We were sent a copy of the PDF referenced in Sean's news post below. Basically, Corsair is claiming that OCZ's new XTC heat spreaders are no more effective than the somewhat standard "flat" heat spreaders used on most high-end modules. Here's a big snip from the PDF...
All our tests used the RST Pro card "Stress Test" to heavily exercise the memory. The tests were
run in one of our qualification ovens at exactly 68 degrees F ambient temperature. Our standard
stability test includes 3 iterations of the RST Pro2 "Burn in" option, with Stuck, Weave, Jump,
Primes, Parity, Pseudo Random, ATS, and Crosstalk turned on. A passing result was considered
to be three consecutive iterations of the stress test with zero errors.
The tests were run using the same physical memory module. After each configuration was tested
the heat spreader and all attachment materials were removed, and the new heat spreader type was attached using its production attachment process. Each test was run not once, but twice, to confirm results. In all cases the second test yielded exactly the same results as the first.
Corsair XMS PRO cast aluminum heat spreader - 254 MHz
Corsair XMS stamped aluminum heat spreader - 253 MHz
OCZ "XTC" mesh heat spreader - 253 MHz
No heat spreader - 250 MHz
As expected, all heat spreader types provided an improvement of a few MHz over the same module with no heat spreader applied. Within the heat spreader results, the XMS PRO provided a small performance gain over the XMS and Mesh heat spreaders. This is the result that we expected to see; the additional surface area provided by the larger heat spreader would naturally be expected to dissipate a nominal amount of additional heat.
Although we haven't verified these results for ourselves, I tend to believe they are correct. The effectiveness of a heatsink / heat-spreader is determined by a few factors, namely its surface area, material, mass, and thermal interface material. OCZ's heat-spreaders may have an advantage in terms of surface area because of the honeycomb design, but they also have a disadvantage in mass. And overall, the need for heat-spreaders on RAM is debatable in the first place.
As usual, what you should do as consumers is read the reviews and buy the products that best suite your needs.