that looks really, really cool. i have significant experience in all the areas you mentioned, and was pretty close to emailing you, when i saw your client app appears to be windows-only. and since it looks like you're using directx, the possibility of a mac port seems slim. i just can't bring myself to sit in front of a windows box all day.
best of luck to you all the same. looks like you've got a winner on your hands.
Our new graphics engine which will be coming out in a couple months is based on the open source Irrlicht graphics engine which is Windows, Linux, and MacOS. We're just going to support Windows at first, but in theory, versions for the other systems should be pretty easy as we're using cross platform sound and networking libraries as well.
I am torn, though, in deciding whether or not to support these other platforms even if the port is quite easy. I don't know if the extra people that it would bring in would be worth the extra QA to maintain three different versions on the client.
best of luck to you all the same. looks like you've got a winner on your hands.