We even had a rapidly adapting network make-and-break recovery layer. You unplug your laptop from a wired connection, switch to wireless - we recovered in milliseconds. You heard barely a click.
The encryption issue is fun - we had a rotate-key message in-band. The receiver loaded new keys and tried them in sequence to ease the turnover time - out-of-order packets etc could make it ambiguous for a short while which key to use. A cache and aging keys out made it work pretty well.
Remixing on user stations proved to be problematic (mentioned elsewhere on this thread). You'd think if 6 people at one site were conferencing with a dozen elsewhere, you could elect one at each site to mix-and-forward. But corporate networks made it hard to determine who was 'adjacent' - they were often layered and without uPNP (is that what the router protocol is called?) you couldn't tell if somebody at the next desk was even in your company.
We had up to 100 people in a conference, and our enter-the-conference time was on the order of 100ms. Click into an all-hands, and be able to hear everybody before you finger left the mouse button. It was wonderful.
Sococo today is a sad shadow of that. They went open-source and lost all our IP instantly. Just another WebRTC client last I knew.