Hi Rich,
With a bit of research I have confirmed what you have reported. SEP's optional Outlook protection works fine with Outlook 2003, 2007, etc but a technology change in 2010 will prevent it from operating as designed.
I have just voted to agree with your Idea at https://www-secure.symantec.com/connect/idea/sep-11-outlook-auto-protect-will-no-longer-work-outlook-2010 and encourage the same from all other community forum members who plan to use Office 2010. The more support this idea receives, the better the chances are that Outlook 2010 support will be included in a future release.
The good news: if a proper mail security program like Symantec Mail Security for MS Exchange (SMSMSE) is installed on the comapny's Exchange server or elsewhere in the mail flow (a dedicated mail scanning appliance, for instance) then any threats or other unwanted content should be cleaned long before the messages reach the end users. SEP's optional mail scanning components are of most use only in very small offices or unmanaged deployments.
Thanks and best regards,
Mick