Photoshop is not really that video card intensive generally. I use Photoshop on a laptop with built in graphics a lot and it's not really and issue at all. If you deal with HUGE files then it might become more important.
There are specific supported cards that do allow the use of OpenGL to speed up some processes, but I don't think I would call it a critical thing to have. This is the list I found:
NVIDIA GeForce 9400M
GeForce 9600M GT,
GeForce 8600M GT,
GeForce GT 120,
GeForce GT 130,
GeForce GTX 285,
GeForce 8800 GT,
GeForce 8800 GS,
Quadro FX 4800,
Quadro FX5600
ATI Radeon HD 4670,
ATI Radeon HD 4850,
Radeon HD 4870
Here is another comment on the acceleration:
When OpenGL is enabled in Photoshop CS5, there are 3 selectable modes available. Basic, Normal and Advanced.
Basic - This mode used the least amount of GPU memory and the most basic OpenGL features. Use this mode when experiencing visual defects or general slowdowns in your document window or when running other applications that preoccupy the GPU.
Normal - THis mode uses a large amount of GPU memory and advanced OPenGL features to perform color matching, tone mapping and checkerboard blending. This frees the CPU to perform other tasks but may cause visual defects on some GPUs.
Advanced - This mode is the most GPU intensive. It uses the same amount of memory as the Normal mode while enabling more advanced techniques to improve drawing performance. This may cause visual defects on some GPUs.
