I think I have it working - Apparently there's no way to create a node called "transparency_map", but image_map seems to have the same settings, and, other than weirdness when I try to use a tif as a texture, it seems to work. I kind of miss the simple one-page materials dialog in P4. Sure, you can do lots more with the new setup, but it takes a lot longer to 'wire' everything up.