Don't know if its already been mentioned but its not so much the calendar as the individual entries that one might one to be private/public....
also, you would probably want to be able to have degrees of visibility. For example as Director I'd probably want certain things private, but visible to co-directors and my PA perhaps (if I had one ;) but not visible to other employees.
So you'd want to be able to create closed-user-groups.
As well... and this is something I've recently been asked by a customer, GSM adn PDA integration is key... SMS notifications of diary changes entries for example, and being able to sync the system.
I guess you;ve already used the SMS Broker, so you'll know it won;t affect the application, other than you should put in the option to put an SMS on the queue at these key points.
If you say PDA/Mobile integration to a customer who want an intranet their eyes light up ;)
