Just when I thought Microsoft had finally seen
the virtue of contributing to an existing standard
Of course, not when they can force their own standard down on people's throats and get away with it, like they did with Direct 3D, which eventually won (on Windows anyway), but if you are talking about HTML5, remember that they tried their luck with Silverlight first.
Ultimately, Microsoft could be better of if they manage to impose their new proprietary wannabe de-facto standard. It doesn't care if it wrecks the whole industry in the process, they care about money.
C++ AMP is based on the DirectCompute APIs in DirectX 11.
My $.02 -- maybe the target audience for C++ AMP is different than the target audience for OpenCL. Before it was released, I really liked the idea of OpenCL but in practice it doesn't really deliver very well (performance-wise) compared to alternatives like nVidia CUDA, AMD APP (formerly Stream), and DirectCompute.
I think people like CUDA because Nvidia puts a serious effort into their development tools and Marketing. That's not meaningless.
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.).