Last week, NVIDIA updated it's CUDA drivers to 5.0 for the Mac, adding support for OS X Mountain Lion and GeForce GT 650M. GeForce GT 650M graphics processors are found in both the latest 15-inch MacBook Pro and the 15-inch MacBook Pro with Retina display. This update should help out anyone that does video encoding on OS X 10.8 as it helps move some of the processing workload from the CPU over to the GPU.
You can find these drivers over at NVIDIA. Let us know how they work on your CustoMac.