The Sheik,
Netinfo is perhaps the most under-documented feature of OS X, and at the same time perhaps the most powerful and useful to know. I have been in the process of trying to teach myself, but it is a long and arduous process. I have, however, learned quite a bit and will be attempting to summize the whole thing in a "how-to" article for MacNET v2.
In the interim, I can point you to a few helpful TILs (IDs: 30832, 60026, and 60032) and at least one man page (man netinfo). There are also several other articles from neXT, but at last check the URLs I had for them no longer work, if I can find them again I will let you know. otherwise, feel free to ask what you want to know specifically and I'll see how weel i've learned this stuff and try and give you an answer.
Ciao!