My Note has this capability as well, subscribed for more info. I think instead of using the CPU to render the images, it ONLY uses the GPU, but I'm not an expert on mobile chips.
Basically it forces the gpu to do all the rendering and takes some of the load off of the cpu. It does make a lot of apps quicker and your transitions are generally smoother. However if any of the apps you use don't support hardware acceleration it will cause them to glitch. Regards battery some people say it improves some say it makes it worse so I really can't help you there