I will not even call this a thinly-veiled rant. Linus admits it. To make a point, he assembled a $5000 PC running a pair of NVIDIA GeForce 780 Ti GPUs and another pair of AMD Radeon R9 290X graphics cards. While Bitcoin mining would likely utilize all four video cards well enough, games will not. Of course, he did not even mention the former application (thankfully).
Honestly, he's right. One of the reasons why I am excited about OpenCL (and its WebCL companion) is that it simply does not care about devices. Your host code manages the application but, when the jobs get dirty, it enlists help from an available accelerator by telling it to perform a kernel (think of it like function) and share the resulting chunk of memory.
This can be an AMD GPU. This can be an NVIDIA GPU. This can be an x86 CPU. This can be an FPGA. If the host has multiple, independent tasks, it can be several of the above (and in any combination). OpenCL really does not care.
Obviously, to be fair, AMD is very receptive to open platforms. NVIDIA is less-so, and they are honest about that, but they conform to standards when it benefits their users more than their proprietary ones. I know that point can be taken multiple ways, and several will be hotly debated, but I really cannot find the words to properly narrow it.
Despite the fragmentation in features, there is one thing to be proud of as a PC gamer. You may have different experiences depending on the components you purchase.
But, at least you will always have an experience.