I think the big secret thing with cuda or opencl clients is that they give one person a decisive advantage over everyone else running only a cpu. Add that with the fact that most users don't know cuda programing (me included) makes for a situation where a cuda client can be valuable to the author... For example artforz has made his own cuda client that has not been released. It has been rumored that he makes up 25% of the generation power on the network. It give him a huge advantage and one I think artforz would like to keep.

The down side to opening up a GPU client to the masses is that it completely kills CPU based generation unless you have a lot of cpus.... On my windows client I went from 4500Khash to 29000khashes.

I will give this a try here in a few days or so on my 8800gtx hackintosh and see how it runs. What GPU does your mac have in it?
I have no cuda or MAC OS X programming knowledge but, I have done some c in BSD and will have a go at the code to see what I might be able to do. Thank you for your efforts!