For those of you with air-cooling this is well worth a read.
http://www.hardwaresecrets.com/article/Which-is-The-Best-Position-for-a-Tower-CPU-Cooler/1815
I wasnt expecting such a large difference. But there you go, it is worthwhile having the heat sink fan facing the gpu.
Be sure to look at the temp benchmarks. It will change how you aircool. I looked at because the new v8 cpucooler has to be mounted that way for amd boards.
Can't be bothered to change position, my CPU temperature doesn't exceed 50 with fan facing memory.