There are numerous theoretical advantages to using the GPU to handle some of the heavy lifting, but theory and practice have a very long history of clashing. So what kind of real world results can we expect?
The primary result after this addition will be that changing extremely large images will have less of a waiting-period [Also known as ‘The Great Wait]. During the demonstration an Adobe employee showed that zooming in, out, and rotating on a canvas the size of 2GB with a 442 mega pixel resolution is smooth and without any amount of wait or lag, also when importing a 3D model into Photoshop Extended, adding text or paint to the 3D object's surface, and the rendering of the new 3D object, all without any type of delay.
We're not certain if this is going to be a Windows-only feature at the moment, but given the somewhat strained relationship between Apple and Adobe these days it would certainly seem possible that Windows systems would not only get 64-bit versions of Adobe products first, but GPU-assisted variants as well.