Best course of action would be to slap a firewall up to prevent unauthorized downloading, agressive email policies (no executable attachments or executable attachments in zip files), ban P2P and other file-sharing programs, and educate your users on "Why It's Not A Good Idea To Download That 3-D Screensaver"...
I see this transformation at Symantec in light of better security in Vista. User Account Control will mean the end of many security services at many security vendors. I view antivirus companies as I do physical security companies in South Africa. I don't trust them! Who knows what they will do to ensure their survival...?