New SDK Features

• High Dynamic Range lighting now supported in the tools
• Day of Defeat: Source support now included
• New Hammer Editor features:
  • VGUI Model browser with real-time 3D view
  • Map autosave/backup
  • Model and displacement rendering in 2D views
  • Many other small improvements and bug fixes

For a full list of changes, see the Source SDK Changelist on the Valve Developer Community site.