Single Sign On is now supported by Google Apps Sync for Outlook. “When you log in, you have the option to log in with your Google Apps account and password, or instead use your company’s SSO authentication if they have enabled that option.” (Google)
Now when you delegate your email and calendar in Google Apps, the person you delegated to has the ability to handle messages, calendar events, answer emails, and create and respond to invitations on your behalf, all from Microsoft’s Outlook client.
Delegation and Single Sign On supported in latest version of Google Apps Sync for Outlook
February 2, 2010