I am still very new to XMPP and OpenFire and even moderately familiar with Java. So I dont understand all the terminologies. Hope to get there in the next few weeks.
Can you explain what you mean by low-level netowrking magic. Are you talking about BSD socket programming at a TCP/IP level. What kind of networking magic are you talking about?
I heard that a company called Nimbuzz uses OpenFire and they claim to have 150 million users. So I dont know how they are handling such a large user base with OpenFire.