Yep, the service pack to the .1 release is here:

• ArcGIS (Desktop, Engine, Server) 9.3.1 Service Pack 1
• ArcSDE 9.3.1 Service Pack 1
• ArcIMS 9.3.1 Service Pack 1
• ArcGIS Image Server 9.3.1 Service Pack 1

UPDATE: Yikes, I left off ArcGIS Military Analyst 9.3.1 Service Pack 1

You can learn more on the “Issues addressed with Service Pack 1” page. I can’t think of any other way to celebrate than dear old Rocky Top…

ArcGIS, you’ll always be home to me…