The problem is this -- go ahead and take that OpenCL code and run it on some non-nVidia hardware. For any reasonably complex code, it turns out that you really

The problem is this -- go ahead and take that OpenCL code and run it on some non-nVidia hardware. For any reasonably complex code, it turns out that you really need to optimize specifically for whatever hardware you're running on. So, while you may be using a standardized API, you still have to write specific versions of your code for each platform that you want to get the best performance on. IMO, developers would rather write against a non-standard API (a la C++ AMP) that ran at a consistently good performance level across all of their targets (nVidia/AMD/Intel GPUs, multicore CPUs, etc.).