I don't like the USB version of the PowerLinc because most of the tools for communicating directly to the PowerLinc only work with the serial version. It's much more complicated to communicate with the USB version.

This link has useful information on using home automation tools with a Mac:

http://w3.misterhouse.net:81/get_to_know_mh.html

Many of the low-level open source tools that I use in the book are written by the author of MisterHouse, so there's a good chance my scripts will work on the Mac if you follow his instructions. I haven't tested it, though.