What, and people haven't been ragging on and even trying to replace OpenGL for years? Everyone used the GPU-specific API rather than OpenGL on PS3 to make it harder to port their code, not to get the maximum possible performance? The "leading game developers" that allegedly inspired Mantle aren't going to show?
Standards are great, and I'd love OpenGL drivers to be as fast as possible, but OpenGL being what it is, this API seems pretty interesting to me.
libgcm is pretty much just OpenGL with a few Sony specific extensions - plus you have to use their headers which use macros to build the command lists, probably pulled right out of NVidia's driver code.
It's quite fascinating how many of the PS3's APIs are wrappers around established standards/libraries, almost as if they were deliberately crafted to require more porting effort from developers.
Standards are great, and I'd love OpenGL drivers to be as fast as possible, but OpenGL being what it is, this API seems pretty interesting to me.