On May 5, 2011 Apple will discontinue MobileMe's Sync Services calendaring system and will force users to upgrade their calendars to CalDAV. CalDAV is a published open standard, which allows for application and platform independence, long term access, accessibility for those with disabilities, and architectural integrity. Sync Services, on the other hand, has been a nightmare due to its syncing failures. Apple has even referred to troubleshooting Sync Services as dealing with a "Swarm of Bees" inside their official knowledge base.
As of this writing, none of the Microsoft calendaring applications support CalDAV. This forces all users of MobileMe and Entourage or Outlook for Mac to create a different approach for the integration.
SOLUTION A - Integrate with Apple
It is possible to bring all of your Exchange, Entourage, our Outlook for Mac calendars in to Apple's Mail, Address Book, and iCal. For full integration with Exchange the machine must be running Snow Leopard.
SOLUTION B - Separate your Activities
If you're more accustomed to working in the Microsoft Office Suites and okay with keeping the two systems separate, it may be be best to separate your professional and personal workflows.
SOLUTION C - Use Third Party Tools
As of this writing it's not possible to fully integrate the Microsoft Office and MobileMe calendars so they sync together into one calendar. There is, however, one application named BusyCal that will allow you to view both calendar types (CalDAV and Sync Services) in one system. Although this is technically possible, it's still not recommended in BusyCal's knowledge base:
"BusyCal does not work well with Entourage. BusyCal is designed to work with Sync Services, which Entourage also supports to a limited degree. You can sync Entourage with Sync Services in Entourage Preferences > Sync Services > "Synchronize events and tasks with iCal and MobileMe". This will create an "Entourage" calendar in iCal and BusyCal containing all of your Entourage events. Once there, you can use BusyCal to sync the Entourage calendar with others on your LAN or with Google Calendar. However, Entourage will only sync that single calendar and will not sync with any of the other calendars in iCal or BusyCal, so it is rather limiting. In addition, Entourage doesn't play well with Sync Services, which may result in duplicate events and other strange behavior. Therefore, it's not recommended that you use BusyCal with Entourage."
At this point, we're confident in recommending both the first and second option to our Pro Support Clients. As the developer of BusyCal isn't even recommending syncing with the Microsoft Office Suites, perhaps it's time for Microsoft to create a new approach using open standards.