We curretnly have multiple Public calendars setup within Exchange on our SBS 2003 server.
Daily service appoinments are entered using the default catagory color code. Once the item has been completed it is manually set to a different catagory color code.
We have 8 workstations accessing the 7 Public calendars. If a user sets an appointment to a new catagory, the change is not seen by the other Outlook users. Each user only sees the appoinments that were changed by them.
This seems to have begun once we upgraded to Outlook 2007.