• New faster drawing map service
  
  • Outperforms ArcGIS 9.3 and equivalent ArcIMS services.
  • Produces significantly better-looking maps.
  • Shortens map caching time.
• New Map Service Publishing toolbar in ArcMap helps you tune-up your map documents before publishing to ArcGIS Server.
  
  • Review and respond to errors, unsupported content, and warnings about items that will slow down your dynamic map services.
  • Preview your map document and estimated rendering time.
  • Save your map document to a map service definition (msd) format, which is optimized for performance in ArcGIS Server.

• Better sharing of layers
  
  • Layers referencing feature or raster data can be packaged into a single layer package comprised of both the layer file and data. A layer package is created in ArcGIS Desktop and encapsulates ArcMap cartography and data. It can easily be e-mailed to others or placed on a DVD or network drive.
• With the ArcGIS Online Web application (beta coming soon), you will be able to
  
  • Search for maps published by ESRI and other users.
  • Upload maps and register online map services.
  • Organize and control access to shared maps.
  • Save Web maps as items for others to share, discover, and use.
  • Share layer packages.

• Quickly start GIS projects with ready-to-use content.
  
  • Up-to-date multi-scale mapping content from Microsoft Virtual Earth includes aerial imagery, roads, and hybrid (aerial with labels) imagery.
  • Content (imagery, roads, and hybrid) appears as another data layer in GIS providing excellent background maps on which users can overlay their operational data.
  • ArcGIS Desktop and ArcGIS Server users directly connect to Microsoft Virtual Earth content via ArcGIS Online.
  • Clients can access Virtual Earth content from any Web applications built with ArcGIS Server and ArcGIS Server Web SDKs (including JavaScript, Flex, and Microsoft Silverlight APIs).

• Ability to extend the ArcGIS/ArcObjects Framework. Java developers can now create the following extensions in their native language:
  
  • Custom geoprocessing tools
  • Server object extensions (SOEs) and utility objects for ArcGIS Server
  • Class extensions for customized data behavior in a geodatabase
  • Custom renderers for customized rendering of data in ArcMap and ArcGIS Engine applications
  • Plug-in data sources
• Tools for debugging, registering and deploying Java extensions for ArcGIS
• Support for Eclipse integrated development environment (IDE)
  
  • Wizards to generate boilerplate code based on the developer's specification
  • Autodeploy feature
    

• Upgrading to ArcGIS 9.3.1 does not require uninstalling ArcGIS 9.3.
• Easy to migrate or work in mixed environments of ArcGIS 9.3 and ArcGIS 9.3.1 within the same organization since geodatabases, map documents, and APIs did not change.

With the release of ArcGIS 9.3.1, the following changes in ArcGIS Server licensing will take effect:

• ArcGIS Server Standard (Workgroup or Enterprise) users will be able to use the editing capabilities of ArcGIS Server.
• ArcGIS Server Advanced (Workgroup or Enterprise) will include the following extensions for no additional fee:
  
  • Spatial
  • 3D
  • Network
  • Geostatistical
• ArcGIS Server Enterprise users will be able to deploy the following components without incurring a deployment license fee:
  
  • Web ADF – SDK or Runtime
  • Web Service Handlers
  • Server Object Manager