[yoklov]

ISPC is cool, what it helps out with (writing the SIMD kernel) has never really been the bottleneck in my experience.

The data still has to be arranged optimally for the hardware in order for SIMD code to have any benefit (and at this point, writing SIMD code is straightforward). You also still need to be experienced with the capabilities of the hardware if you have any chance of writing good ISPC code (although this is true of C, as well as any shading language).

That said, using it to target SSE and AVX with the same code is attractive.