Here is my understanding:
Nvidia and ATI cards do not have much decoding on-board. With most top video cards recently introduced second decoder inside GPU, and I believe you still limited with 1080p resolution.
Intel HD graphics are different with QuickSych. However it is windows only and, more importantly, monitor must be connected to this video card in order to make QuickSych available. So average laptop with second, third and forth gen of iX processor having external (extra ATI or NVIDIA) video card has no QuickSych, regardless of the fact chip is in place.
However GPU is still very useful for VMS to unload some operation from CPU rather than decoding, such as: color transformation (you know all this MPEGs/JPEG is YUV and needs to be transformed to RGB to be displayed). And of cause DEWARPING is perfect for any GPU.
We (Network Optix) use GPU a lot.