Thanks for the note. In my opinion the articles give a pretty complete beginning introduction to the subject. I wrote them when I was trying to figure out digital certificates and openvpn and could not find all of the basic info in one single place. As such, the articles are general and simplified. I do think that you could use the setup outlined in the tutorial in a small shop with a few permanent users that are not coming or going and where the data stored on the network was not sensative. That is, if you are experienced and can devote the time and energy.
I think that in a larger network where new users are constantly being added and removed and where the network may hold sensative data, the skill and knowlege of the administrator is critical. A commercial package may be a good choice there, and after reading the articles and working the code examples you will have the knowledge to help you make a good choice. I cannot answer your question more fully thant to say that the Internet and OReilly's site is full of security related articles.