Well technically it's multi-GPU, so if you're running a working GeForce 7950 GX2 or one of those bizarre contraptions ASUS and Gigabyte use to put together, then this includes you as well.
The patch, aimed at PCs running Windows Vista only, addresses a scheduling problem within the DirectX kernel. Here's the technobabble, which I'll attempt to decipher:
A graphics processing unit (GPU) or part of a GPU link may incur a small scheduling latency on a new Direct Memory Access (DMA) packet. This is true if the DMA packet is submitted to the GPU that has previously run out of work and if another GPU in the linked configuration is very busy. In some scenarios, significant starvation of one or more GPUs in the linked configuration reduces the expected performance of an application.
Essentially, it's a load-balancing thing - the hotfix spreads the work evenly among the GPUs. It's unclear whether this affects both Direct3D 10 and Direct3D 9 games - Microsoft hasn't provided enough information to make a solid call.
The link below is for the Knowledge Base article. If you want the hotfix, I'd suggest trying elsewhere (every couple of hours) or waiting for Service Pack 1.