I can't believe this. VLC does not use 70% CPU to decode a 720p video, and it's not using any hardware acceleration other than an overlay. (Or maybe it renders to a texture; either way, it works fine even with a GMA950.)
It also appears that vidix supports OS X, which lets you actually offload video decoding to your nVidia card. (Edit: maybe I'm wrong, I was thinking of VDPAU, not vidix.)
So... I call "LIES" on this. Apple loves arbitrary restrictions, but OS X does not have many. You can make your GPU do whatever you want, even on Apple hardware.