Funny, just yesterday I checked out the new generation of Nvidia gfx cards (kepler) and they were talking about how good they are for raytracing.
DACRT does indeed look interesting. I wonder how well this would work with sorting algorithms other than quicksort. A while back I was playing with an idea to use radix sort to build a hirarchical structure that can be used for raytracing. E.g. a point in space would fit into some space in an octree. Instead of using the x,y,z coordinates of the pixel, you could store the node indices and then sort them to get an optimised structure to use with OpenCL. This way you would be able to have moving objects in a scene since they can arbitrarily change their location bevore beeing sorted. But in the end... who has the time... I had to put the porject to rest