I've just bitten the bullet and upgraded from MS Office 2004 (for the Mac) to Office 2008. I actually prefer NeoOffice and Thunderbird, but we use Exchange for our corporate email and I am desperate for better calendar and address book support.
I can now check colleagues availability when making appointments, however I can't view shared calendars.
At the moment it keeps asking for access to my keychain every 10 mins and the normal fix does not work :-(
So far I can't access our global address book either.
I wish we used Zimbra!