Beau,
Most everything you could need to know is in the man pages for yum. If you have specific questions not answered by the man pages, please feel free to ask me for my experiences, Seth (who wrote the thing so should be able to answer *anything* about it), or the list.
I'm actually a Debian developer myself, but we're using CentOS at work, and I find yum quite comfortable (and a good deal less complex than apt for setting up and maintaining local repositories).
I've recently implemented the use of the yumgroups.xml file to define groups of packages for installation on different classes of machines. It works very well (provided you make sure that all the important files are actually readable!).
Claire