Does any OS X hardware contain on chip h.264 encoding/decoding? I know that iOS devices have the h.264 instruction set on chip, which helps to dramatically reduce processing (and thus, power, battery drain, etc.) when watching native video.

Has this been added to Intel CPUs, or ATI/nVidia GPUs, in Apple's Desktop/Laptop hardware?
Apple's own apps on OSX has video acceleration support for years, provided by the GPU. h.264 hardware video acceleration is available to 3rd-party apps via the Video Decode Acceleration Framework since OSX 10.6.3. See:

http://developer.apple.com/library/mac/#technotes/tn2267/_index.html

http://arstechnica.com/apple/2008/10/digging-into-new-macbooks-support-of-gpu-accelerated-h-264/

http://xbmc.org/davilla/2010/05/03/osx-gets-h-264-accelleration/