Microsoft Outlook Auto-Protect: Is it worthwhile?

I'm trying to figure out if the outlook protection function under virus protection policy->email scans is worth using.  Here’s all I see in manual regarding the outlook add-in. Downloads incoming Microsoft Outlook email attachments and scans for viruses and security risks when the user reads the message and opens the attachment. Based on this definition this seems to duplicate the file system AV functionality but it will catch a malicious file before the user opens it.  So it is worth it?

We tested it and had some compatibility issues with users who like to modify message subject lines in shared/group mailboxes and have disabled this feature.

Comments?  Thanks.  Paul