Another issue is that many large organizations already have a separate iCalendar-compliant calendaring server, and what you really want is for OpenACS to use that server as its data store, instead of storing it in the OpenACS data model. That way you can view and manage your calendar through OpenACS, through Outlook, as well as through any other piece of software on your intranet who knows how to speak with the iCal server.
Wasn't this what Talli's Momentum project was about?
See also this U Washington project.
