InsideHW.com has compared performances of Intel Core i7 for dual and triple channel memory mode. Here's a bit:

After we finished tests in triple channel mode we proceeded to dual channel mode test. First test that we run was Everest and we were really shocked with results. It was clear that memory access was faster in case of dual channel memory mode while bandwidth had very close values. After Everest we were slightly less shocked with results that provided WinRAR test that is very sensitive to memory subsystem performances. It showed only 2-3% difference in performances in favor of dual channel mode. Better performance of dual channel mode showed also DivX test where our test showed 3% performance difference in favor of dual channel mode also. Then we started Blender that showed minor differences between system operating in dual and triple channel memory mode. Nuclear MC also showed minor differences between two memory modes tested here, while 3DMark06 showed almost identical results. We all know that Crysis can react positively in case of better memory performances so results weren't that much of a surprise. World in Conflict also showed differences in performance levels of both memory modes. Both gaming tests favored system that operated in triple channel mode.

After all these tests you need to ask yourself: What the heck is that triple channel mode useful for anyway, when it is obvious that is doesn't provide performance boost that is expected? Maybe in the future and with some new versions of memory controllers, triple channel mode will provide better performances so transition to this platform will make more sense. Until that moment triple channel mode will be just another nice sticker on LGA 1366 motherboards and memory packages. Of course memory manufacturers already have triple channel DDR3 kits that are intended to be used on Intel Core i7 platform. Since these are triple channel kits they have three DDR3 modules with total capacity of 3GB or 6GB. Since prices for DDR3 memory are still pretty high it is obvious who will profit the most from this situation where (uninformed) users will go for triple channel kits with intention to use up potentials of their new platform.