After forcing a quit after 13 hrs on what should not have been that involved I decided to do some experimenting.
Doing a series of renders changing one setting at a time and comparing render time is giving me an idea of what tweaks are taking the power.
Also, opening the activity monitor provides a little insight into what the application is doing.
Using Radiosity seems to be a real killer. Without it the CPU will be running at near capacity. Anti-aliasing following takes about 5X as long to render as the basic Anti-aliasing with shadows. But turn on Radiosity and the CPU only operates at about 50% capacity and I have yet the be patient enough to finish a render with it.