The company I work for have implemented a Sharepoint server as an intranet recently. On the whole, I consider it an excellent piece of software and a formidable solution in flexibility and capability.
BUT there is one enormous flaw with it: Calendar sharing.
This is quoted from the Microsoft Powerpoint document for Sharepoint integration:
“Note  When you connect resources to Outlook 2007, the resources appear in their respective sections of the Outlook 2007 navigation pane. Calendars appear in the Calendar pane, under Other Calendars; Tasks appear in the Tasks pane, under Other Tasks; Contact Lists appear in the Contacts pane, under Other Contacts. Discussion Lists are similar to Document Libraries and appear in the Mail pane, under SharePoint Lists.”

written by Pensive