Hi Gerald,
that seems to be rooted in the MS protocol. You can define "task lists" in a MOSS site, these are shown in the task pane in MS Office 2007. This way, you only see those tasks, that are MOSS related.
Outlook Tasks or Alfresco tasks are kept in a different places and are not integrated.
Talking of show stopper - it depends on which clients the people are supposed to use with Alfresco repository. If you work in Office exclusively, maybe "SHARE" client, that should suffice, otherwise, you will have to code.
Norgan