Maybe I didn't clarify what the problem was...
Shared calendaring is working great and I have that all setup, I can create, view, modify (some info).. The problem is moving an appointment from UserA to UserB... It simply doesn't work..
This is all done through the WebUI no connectors in use here..
I've been digging around on the forums and it looks like this is a known bug as described in this topic -
Managing shared calendars Bug 7129 - cannot move existing appt/message/etc. to another user's mailbox
Which I find disappointing, as it would seem to be a very common task for a collaboration suite. Hopefully it will be addressed/fixed in the next release. For now it looks like we'll have to put up with copy/paste info to notepad then back to zimbra in order to move an appointment from one tech's schedule to the next.